Air pollution

Air pollution occurs when gases, dust particles, fumes (or smoke) or odour are introduced into the atmosphere in a way that makes it harmful to humans, animals and plant.

There are two types of pollutants:
Primary pollutants are those gases or particles that are pumped into the air to make it unclean. They include carbon monoxide from automobile (cars) exhausts and sulfur dioxide from the combustion of coal.

Secondary pollutants: When pollutants in the air mix up in a chemical reaction, they form an even more dangerous chemical. Examples of a secondary pollutant include ozone, which is formed when hydrocarbons (HC) and nitrogen oxides (NOx) combine in the presence of sunlight; NO2, which is formed as NO combines with oxygen in the air; and acid rain, which is formed when sulfur dioxide or nitrogen oxides react with water.

What causes air pollution?

Air pollution can result from both human and natural actions. Natural events that pollute the air include forest fires, volcanic eruptions, wind erosion, pollen dispersal, evaporation of organic compounds and natural radioactivity. Pollution from natural occurrences are not very often.

Human activities that result in air pollution include:

1. Emissions from industries and manufacturing activities

2. Burning Fossil Fuels

3. Household and Farming Chemicals

Carbon Monoxide (CO)

Carbon monoxide (CO) is a colourless, odourless gas that is produced by the incomplete burning of carbon-based fuels including petrol, diesel, and wood. It is also produced from the combustion of natural and synthetic products such as cigarettes.

Effects: Carbon monoxide enters the bloodstream and reduces oxygen delivery to the body's organs and tissues. The health threat from CO is most serious for those who suffer from cardiovascular disease. Healthy individuals are also affected, but only at higher levels of exposure. Exposure to elevated CO levels is associated with visual impairment, reduced work capacity, reduced manual dexterity, poor learning ability, and difficulty in performing complex tasks.

Sulfur Dioxide (SO2)

Sulphur dioxide (SO₂) is a gas produced from burning coal, mainly in thermal power plants. Some industrial processes, such as production of paper and smelting of metals, produce sulphur dioxide. It is a major contributor to smog and acid rain.

Effects: The major health concerns associated with exposure to high concentrations of SO2 include effects on breathing, respiratory illness, alterations in pulmonary defenses, and aggravation of existing cardiovascular disease. Major subgroups of the population that are most sensitive to SO2 include asthmatics and individuals with cardiovascular disease or chronic lung disease.

Nitrogen Oxides (NOx)

Nitrogen oxide (Nox) causes smog and acid rain. These gases form when fuel is burned at high temperatures, and come principally from motor vehicle exhaust and stationary sources such as electric utilities and industrial boilers. A suffocating, brownish gas, nitrogen dioxide is a strong oxidizing agent that reacts in the air to form corrosive nitric acid, as well as toxic organic nitrates.

Nitrogen dioxide can irritate the lungs and lower resistance to respiratory infections such as influenza. The effects of short-term exposure are still unclear, but continued or frequent exposure to concentrations that are typically much higher than those normally found in the ambient air may cause increased incidence of acute respiratory illness in children.

Ozone (O3)

Ozone occur naturally in the upper layers of the atmosphere. This important gas shields the earth from the harmful ultraviolet rays of the sun. However, at the ground level, it is a pollutant with highly toxic effects. Vehicles and industries are the major source of ground-level ozone emissions. When sunlight and its heat react with these gases and fine particles in the atmosphere, smog is formed. It is purely caused by air pollution. Ground level ozone and fine particles are released in the air due to complex photochemical reactions between volatile organic compounds (VOC), sulphur dioxide (SO₂) and nitrogen oxides (NO_x). These VOC, SO₂ and NO_x are called precursors. The main sources of these precursors are pollutants released directly into the air by gasoline and diesel-run vehicles, industrial plants and activities, and heating due to human activities.

Effects: Because of the effects of ozone on lungs, smog exposure may lead to several different types of short-term health problems:

Coughing and throat/chest irritation: High levels of ozone can irritate respiratory system. Generally, these types of mild symptoms only last for a few hours after been exposed to smog. However, ozone can continue to harm lungs even after symptoms disappear.
Worsening asthma symptoms: If you suffer from asthma, being exposed to high levels of ozone from smog can trigger asthma attacks.
Difficulty breathing and lung damage: Because of ozone's effect on lung function, smog can make it feel difficult to breathe deeply, especially during exercise. Research has shown that ozone exposure can also damage the lining of your lungs.

Lead (Pb)

Lead is present in petrol, diesel, lead batteries, paints, hair dye products, etc. Smelters and battery plants are the major sources of the pollutant "lead" in the air.

Effects:

Children

In children, lead is most damaging when they are six years and younger. Even at low levels, lead can be harmful and be associated with:

Learning disabilities resulting in a decreased intelligence (decreased IQ)
Attention deficit disorder
Behavior issues
Nervous system damage
Speech and language impairment
Decreased muscle growth
Decreased bone growth
Kidney damage

High levels of lead are life threatening and can cause seizures, unconsciousness, and death.

Adults

High levels of lead can cause:

Increased chance of illness during pregnancy
Harm to a fetus, including brain damage or death
Fertility problems in both men and women
High blood pressure
Digestive issues
Nerve disorders
Memory and concentration problems
Muscle and joint pain

Particulate Matter

Suspended particulate matter (SPM) consists of solids in the air in the form of smoke, dust, and vapour that can remain suspended for extended periods and is also the main source of haze which reduces visibility. Particles originate from a variety of mobile and stationary sources (diesel trucks, wood stoves, power plants, etc.), their chemical and physical compositions vary widely.

Effects: Major concerns for human health from exposure to particulate matter are: effects on breathing and respiratory systems, damage to lung tissue, cancer, and premature death. The elderly, children, and people with chronic lung disease, influenza, or asthma, tend to be especially sensitive to the effects of particulate matter.

Noise Pollution

Sound is essential to our daily lives, but noise is not. Noise is generally used as an unwanted sound, or sound which produces unpleasant effects and discomfort on the ears.

What are the sources of noise pollution?

Household sources:
Gadgets like food mixer, grinder, vacuum cleaner, washing machine and dryer, cooler, air conditioners, can be very noisy and injurious to health. Others include loud speakers of sound systems and TVs, ipods and ear phones.

Social events:
Places of worship, discos and gigs, parties and other social events also create a lot of noise for the people living in that area. In many market areas, people sell with loud speakers, others shout out offers and try to get customers to buy their goods.

Commercial and industrial activities:
Printing presses, manufacturing industries, construction sites, contribute to noise pollutions in large cities. People who work with lawn mowers, tractors and noisy equipment are also required to wear noise-proof gadgets.

Transportation:
Aero planes flying over houses close to busy, over ground and underground trains, vehicles on road—these are constantly making a lot of noise.

Effects of noise pollution

Generally, problems caused by noise pollution include stress related illnesses, speech interference, hearing loss, sleep disruption, and lost productivity.

Hearing
The immediate and acute effect of noise pollution to a person, over a period of time, is impairment of hearing. Prolonged exposure to impulsive noise to a person will damage their eardrum, which may result in a permanent hearing.

Effects on general health
Health effects of noise include anxiety and stress reaction and in extreme cases fright. The physiological manifestations are headaches, irritability and nervousness, feeling of fatigue and decreases work efficiency

Noise pollution prevention and control

Construction of soundproof rooms for noisy machines in industrial and manufacturing installations must be encouraged. This is also important for residential building—noisy machines should be installed far from sleeping and living rooms, like in a basement or garage.

Use of horns with jarring sounds, motorbikes with damaged exhaust pipes, noisy trucks to be banned.

Noise producing industries, airports, bus and transport terminals and railway stations to sighted far from where living places.

Community law enforcers should check the misuse of loudspeakers, worshipers, outdoor parties and discos, as well as public announcements systems.

Community laws must silence zones near schools / colleges, hospitals etc.

Vegetation (trees) along roads and in residential areas is a good way to reduce noise pollution as they absorb sound.

Water pollution

Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans, aquifers and groundwater), very often by human activities.
Water pollution occurs when pollutants (particles, chemicals or substances that make water contaminated) are discharged directly or indirectly into water bodies without enough treatment to get rid of harmful compounds.

Types of water pollution

There are many types of water pollution because water comes from many sources. Here are a few types of water pollution:

Nutrients Pollution
2. Surface water pollution
3. Oxygen Depleting
4. Ground water pollution
5. Microbiological
6. Suspended Matter
7. Chemical Water Pollution
8. Oil Spillage

9. Industrial waste-Industries cause huge water pollution with their activities.

Effects of water pollution.

Death of aquatic (water) animals
The main problem caused by water pollution is that it kills life that depends on these water bodies. Dead fish, crabs, birds and sea gulls, dolphins, and many other animals often wind up on beaches, killed by pollutants in their habitat (living environment).

Disruption of food-chains
Pollution disrupts the natural food chain as well. Pollutants such as lead and cadmium are eaten by tiny animals. Later, these animals are consumed by fish and shellfish, and the food chain continues to be disrupted at all higher levels.

Diseases
Eventually, humans are affected by this process as well. People can get diseases such as hepatitis by eating seafood that has been poisoned.

Destruction of ecosystems
Ecosystems (the interaction of living things in a place, depending on each other for life) can be severely changed or destroyed by water pollution. Many areas are now being affected by careless human pollution, and this pollution is coming back to hurt humans in many ways.

Prevention of water pollution.

Never throw rubbish away anyhow. Always look for the correct waste bin. If there is none around, please take it home and put it in your trash can. This includes places like the beach, riverside and water bodies.

Use water wisely. Do not keep the tap running when not in use. Also, you can reduce the amount of water you use in washing and bathing. If we all do this, we can significantly prevent water shortages and reduce the amount of dirty water that needs treatment.

Do not throw chemicals, oils, paints and medicines down the sink drain, or the toilet. In many cities, your local environment office can help with the disposal of medicines and chemicals. Check with your local authorities if there is a chemical disposal plan for local residents.

Buy more environmentally safe cleaning liquids for use at home and other public places. They are less dangerous to the environment.

If you use chemicals and pesticides for your gardens and farms, be mindful not to overuse pesticides and fertilizers. This will reduce runoffs of the chemical into nearby water sources. Start looking at options of composting and using organic manure instead.

If you live close to a water body, try to plant lots of trees and flowers around your home, so that when it rains, chemicals from your home does not easily drain into the water.

Governments, local councils and laws
Many governments have very strict laws that help minimize water pollution. These laws are usually directed at industries, hospitals, schools and market areas on how to dispose, treat and manage sewage.

Land pollution

Land pollution is the deterioration (destruction) of the earth’s land surfaces, often directly or indirectly as a result of man’s activities and their misuse of land resources.

Sources of land pollution.

Agricultural sources:
These include waste matter produced by crop, animal manure, and farm residues. They also include the chemical left over of all pesticides, fertilisers and insecticides used for agricultural activities.

Ashes: The residual matter that remains after solid fuels are burned. When waste is burned in incinerators, two types of ashes are produced. Bottom ash is the debris from burnt metal and glass waste. Bottom ash are not bio-degradable. The second type of ash is called fly ash. Ashes easily leak into the soil and water tables causing land and water pollution.

Mining sources: Mining and forestry activities that clear the land surfaces (clearcutting) and use 'skid trails' often leave leave the land unrestored. The surface is exposed to erosion which destroys the quality of the land

Industrial sources: These include paints, chemicals, metals and aluminum, plastics and so on that are produces in the process of manufacturing goods.

Sewage Treatment: Wastes that are left over after sewage has been treated, biomass sludge, and settled solids. Some of these are sent directly to landfills whiles other treatment plants burn them to generate electricity. Both end up polluting the environment.

Garbage or waste: These include household or municipal waste such as glass, metal, cloth, plastic, wood, paper, and so on. Some of these can decay and others cannot. They are usually collected and sent to landfills where the pollution action begins.

Construction sources: These include waste like debris, wood, metals and plastics that are produced from construction activities.

Deforestation: This is when trees are cut down for economic purposes, mining, farming and construction.

Chemical And Nuclear Plants: These include chemical waste from chemical industries that are disposed off into landfills.

Oil Refineries: When crude oil is refined into usable petro, gas or diesel, there are by products that end up as waste.

Effects of land pollution.

Contaminated lands and environments can:

Cause problems in the human respiratory system.

Cause problems on the skin.

Cause various kinds of cancers.

The toxic materials that pollute the soil can get into the human body directly by:

Coming into contact with the skin.

Being washed into water sources like reservoirs and rivers.

Eating fruits and vegetables that have been grown in polluted soil.

Breathing in polluted dust or particles.

Dump sites and landfills also come with serious problems like

Very bad smell and odour in the town.

Landfills breed rodents like rats, mice and insects, who in-turn transmit diseases.

Landfills in towns do not attract tourists to the town. The town will loose revenue.

Many landfills are always burning and they cause further air pollution.

Control of Soil Pollution

1. Use of pesticides should be minimized.
2. Use of fertilisers should be judicious.
3. Cropping techniques should be improved to prevent growth of weeds.
4. Special pits should be selected for dumping wastes. 5. Controlled grazing and forest management.
6. Wind breaks and wind shield in areas exposed to wind erosin
7. Planning of soil binding grasses along banks and slopes prone to rapid erosin.
8. Afforestation and reforestation.

Classification of waste

Generally, waste could be liquid or solid waste. Both of them could be hazardous. Liquid and solid waste types can also be grouped into organic, re-usable and recyclable waste.
Let us see some details below:

Liquid type:
Waste can come in non-solid form. Some solid waste can also be converted to a liquid waste form for disposal. It includes point source and non-point source discharges such as storm water and wastewater. Examples of liquid waste include wash water from homes, liquids used for cleaning in industries and waste detergents.

Solid type:
Solid waste predominantly, is any garbage, refuse or rubbish that we make in our homes and other places. These include old car tires, old newspapers, broken furniture and even food waste. They may include any waste that is non-liquid.

Hazardous type:
Hazardous or harmful waste are those that potentially threaten public health or the environment. Such waste could be inflammable (can easily catch fire), reactive (can easily explode), corrosive (can easily eat through metal) or toxic (poisonous to human and animals). In many countries, it is required by law to involve the appropriate authority to supervise the disposal of such hazardous waste. Examples include fire extinguishers, old propane tanks, pesticides, mercury-containing equipment (e.g, thermostats) and lamps (e.g. fluorescent bulbs) and batteries.

Organic type:

Organic waste comes from plants or animals sources. Commonly, they include food waste, fruit and vegetable peels, flower trimmings and even dog poop can be classified as organic waste. They are biodegradable (this means they are easily broken down by other organisms over time and turned into manure).

Recyclable type:
Recycling is processing used materials (waste) into new, useful products. This is done to reduce the use of raw materials that would have been used. Waste that can be potentially recycled is termed "Recyclable waste". Aluminum products (like soda, milk and tomato cans), Plastics (grocery shopping bags, plastic bottles), Glass products (like wine and beer bottles, broken glass), Paper products (used envelopes, newspapers and magazines, cardboard boxes) can be recycled and fall into this category.

Types of solid waste

Solid waste can be classified into different types depending on their source:
a) Household waste is generally classified as municipal waste,
b) Industrial waste as hazardous waste, and
c) Biomedical waste or hospital waste as infectious waste.

Municipal solid waste

Municipal solid waste consists of household waste, construction and demolition debris, sanitation residue, and waste from streets. This garbage is generated mainly from residential and commercial complexes. With rising urbanization and change in lifestyle and food habits, the amount of municipal solid waste has been increasing rapidly and its composition changing. More than 25% of the municipal solid waste is not collected at all; 70% of the Indian cities lack adequate capacity to transport it and there are no sanitary landfills to dispose of the waste.

Hazardous waste

Industrial and hospital waste is considered hazardous as they may contain toxic substances. Certain types of household waste are also hazardous. Hazardous wastes could be highly toxic to humans, animals, and plants; are corrosive, highly inflammable, or explosive; and react when exposed to certain things e.g. gases. Household waste that can be categorized as hazardous waste include old batteries, shoe polish, paint tins, old medicines, and medicine bottles.

Hospital waste contaminated by chemicals used in hospitals is considered hazardous. These chemicals include formaldehyde and phenols, which are used as disinfectants, and mercury, which is used in thermometers or equipment that measure blood pressure.

In the industrial sector, the major generators of hazardous waste are the metal, chemical, paper, pesticide, dye, refining, and rubber goods industries.

Direct exposure to chemicals in hazardous waste such as mercury and cyanide can be fatal.

Hospital waste

Hospital waste is generated during the diagnosis, treatment, or immunization of human beings or animals or in research activities in these fields or in the production or testing of biologicals. It may include wastes like sharps, soiled waste, disposables, anatomical waste, cultures, discarded medicines, chemical wastes, etc. These are in the form of disposable syringes, swabs, bandages, body fluids, human excreta, etc. This waste is highly infectious and can be a serious threat to human health if not managed in a scientific and discriminate manner.

DISPOSAL METHODS

Waste management simply means the collection, transport, processing or disposal, managing and monitoring of waste materials to minimize its' consequences on humans and environment.

How is waste treated and disposed off?

Waste management simply means the collection, transport, processing or disposal, managing and monitoring of waste materials to minimize its' consequences on humans and environment.

Incineration method of waste management:
This simply means burning waste. This method is common in countries with limited landfill space. Incineration chambers can be small for domestic use, but ther are large ones for municipal use as well. It is great for treating waste with contamination (like those from hospitals) and hazardous waste from factories, but the method produces too much carbon dioxide.

Sanitary Landfills as waste disposal:
Generally, this term means a large piece of land away from living places where all the waste from a town is deposited. But there is more to landfills. Proper landfill management involves sorting out all the waste (waste separation), and sending only the waste that cannot be recycled and composted to the site.

Proper landfills, are also lined at the bottom to minimize the leakage of soil pollutants and other toxins from getting into the water table. This method is effective, but expensive and difficult.

Composting operations of solid wastes include preparing refuse and degrading organic matter by aerobic microorganisms. Refuse is presorted, to remove materials that might have salvage value or cannot be composted, and is ground up to improve the efficiency of the decomposition process.

Recycling

Today, recyclable materials are recovered from municipal refuse by a number of methods, including shredding, magnetic separation of metals, air classification that separates light and heavy fractions, screening, and washing. Another method of recovery is the wet pulping process: Incoming refuse is mixed with water and ground into a slurry in the wet pulper, which resembles a large kitchen disposal unit. Large pieces of metal and other nonpulpable materials are pulled out by a magnetic device before the slurry from the pulper is loaded into a centrifuge called a liquid cyclone. Increasingly, municipalities and private refuse-collection organizations are requiring those who generate solid waste to keep bottles, cans, newspapers, cardboard, and other recyclable items separate from other waste.

Classification of Hazardous waste

Listed Wastes: Wastes that EPA has determined are hazardous. The lists include the F-list (wastes from common manufacturing and industrial processes), K-list (wastes from specific industries), and P- and U-lists (wastes from commercial chemical products).

Characteristic Wastes: Wastes that do not meet any of the listings above but that exhibit ignitability, corrosivity, reactivity, or toxicity.

Universal Wastes: Batteries, pesticides, mercury-containing equipment (e.g., thermostats) and lamps (e.g., fluorescent bulbs).

Mixed Wastes: Waste that contains both radioactive and hazardous waste components.

Waste Identification Process: Details about the process for identifying, characterizing, listing, and delisting hazardous wastes.

Class	Description	Waste Number
A: Wastes with cyanide
Wastes with cyanide	Waste containing cyanide with a concentration >200 ppm in liquid waste	A101
B: Acid wastes
Sulfuric acid	Sulfuric acid with pH =< 2.0	B201
Hydrochloric acid	Hydrochloric acid with pH =< 2.0	B202
Nitric acid	Nitric acid with pH =< 2.0	B203
Phosphoric acid	Phosphoric acid with pH =< 2.0	B204
Hydrofluoric acid	Hydrofluoric acid with pH =< 2.0	B205
Mixture of sulfuric and hydrochloric acid	Mixture of sulfuric and hydrochloric acid with pH =< 2.0	B206
Other inorganic acid	Other inorganic acid with pH =< 2.0	B207
Organic acid	Organic acid with pH =< 2.0	B208
Other acid wastes	Acid wastes other than B201 to B208 with pH =< 2.0	B299
C: Alkali wastes
Caustic soda	Caustic soda with pH >= 12.5	C301
Potash	Potash with pH >= 12.5	C302
Alkaline cleaners	Alkaline cleaners with pH >= 12.5	C303
Ammonium hydroxide	Ammonium hydroxide with pH >= 12.5	C304
Lime slurries	Lime slurries with pH >= 12.5	C305
Other alkali wastes	Alkali wastes other than C301 to C306 pH >=12.5	C399
D: Wastes with inorganic chemicals
Selenium and its compounds	Includes all wastes with a total Se concentration > 1.0 mg/L based on analysis of an extract	D401
Arsenic and its compounds	Includes all wastes with a total As concentration > 5 mg/L based on analysis of an extract	D402
Barium and its compounds	Includes all wastes with a total Ba concentration > 100 mg/L based on analysis of an extract	D403
Cadmium and its compounds	Includes all wastes with a total Cd concentration > 5 mg/l based on analysis of an extract	D404
Chromium compounds	Includes all wastes with a total Cr concentration > 5 mg/l based on analysis of an extract	D405
Lead compounds	Includes all wastes with a total Pb concentration > 5 mg/l based on analysis of an extract	D406
Mercury and mercury compounds	Includes all wastes with a total Hg concentration > 0.2 mg/l based on analysis of an extract. These also includes organomercury compounds. Refer to CCO.	D407
Other wastes with inorganic chemicals	Wastes containing the following chemicals: - antimony and its compounds; - beryllium and its compounds; - metal carbonyls ; - copper compounds; - zinc compounds ; - tellurium and its compounds; - thallium and its compounds; - inorganic fluorine compounds excluding calcium fluoride	D499

Wastewater Characteristics

I.  Physical characteristics

A. total solids content: solid residual matter that remains after evaporation.

By dividing this value into two sub-categories described below: suspended solids and filterable solids.

1. suspended solids: this includes solids that are basically larger than1 micron in diameter.

When we flush the toilet, the fecal wastes have to go somewhere! Such wastes are, of course, part of the suspended solids. These wastes break up fairly quickly due to the action of water during transport. While fecal wastes are certainly part of this group, there may be many other sources (e.g., industrial wastes) depending on the sources of wastewater.

settleable solids: removed by gravity (usually in about one hour).

This is a sub-category of suspended solids. It is useful for us to know how much of the suspended solids will settle out in an hour, because these wastes are the easiest to remove.

2. filterable solids: This includes solids that are basically less than 1 micron in diameter.

These solids are much more difficult to remove from wastewater, because smaller particulates can remain suspended in water for a much longer time. In fact, they can pass through wastewater treatment facilities relatively unchanged. They generally fall into two sub-categories: colloidal and dissolved solids.

colloidal solids: This generally includes solids between 1 - 100 millimicrons in diameter.

dissolved solids: This generally includes wastes less than 1 millimicron in diamter.

II. Chemical characteristics

This refers to the amount of oxygen it takes to break down these organic wastes. In other words, instead of measuring all of the individual organic compounds, we have a general indicator (oxygen) for the strength of these wastes.

A. BOD (Biochemical Oxygen Demand)

a measure of dissolved oxygen used by micro-organisms in the biological oxidation of organic matter.

BOD is perhaps the most relevant measure of organics, because most treatment methods for organic wastes involve the use of microbes to digest the wastes.

B. COD (Chemical Oxygen Demand)

a measure of dissolved oxygen used by an chemical oxidizing agent (potassium dichromate) in the chemical oxidation of organic matter.

COD is faster than BOD, because a powerful chemical oxidizing agent can oxidize organics faster than microbes. This makes it a more convenient measure, but less relevant to many treament methods.

COD is generally higher than BOD, because there are some organics that cannot be digested by microbes, but can be oxidized by powerful chemical agents.

C. TOD (Total Oxygen Demand)

a measure of oxygen used in the incineration (physical oxidation) of organic matter.

This is typically achieved by injecting wastes into a platinum catalyzed combustion chamber, where we measure the amount of oxygen present before and after incineration. The incineration techniques are the fastest of all. It's a useful measurement technique, but in terms of practical treatment methods, we would never actually be able to incinerate millions of gallons of wastewater every day.

D. TOC (Total Organic Carbon)

a measure of the carbon that remains after the incineration (physical oxidation) of organic matter.

Instead of using oxygen as the unit of measure, carbon becomes the unit of measure for this method, mostly from carbon dioxide that remains after complete combustion. We can measure this by infrared techniques. TOC is often used in the various models that predict the fate of different wastes, because it represents a more direct measure of the organics (i.e., all organics are composed of carbon).

Water Pollutants

Major water pollutants are as follows:

Sewage - Sewage pollutants include domestic and hospital wastes, animal and human excreta etc. The sewage let off causes oxygen depletion, spread of diseases/epidemics.

Metals - Metals like mercury are let off into water bodies from industries. Heavy metals like mercury cause poisoning and affect health causing numbness of tongue, lips, limbs,deafness, blurred vision and mental disorders.

Lead - Industrial wastes also lead to Lead pollution. If lead enters the human body system in higher quantities it affects RBCs, bone, brain, liver, kidney and the nervous system. Severe lead poisoning can also lead to coma and death.

Cadmium - Source for cadmium pollution is industries, fertilizers. Cadmium gets deposited in visceral organs like liver, pancreas, kidney, intestinal mucosa etc. Cadmium poisoning causes vomiting, headache, bronchial pneumonia, kidney necrosis, etc.

Arsenic - Fertilizers are source for arsenic pollution. Arsenic poisoning causes renal failure and death. It also causes liver and kidney disorders, nervous disorders and muscular atrophy, etc.

Agrochemicals like DDT - It is a pesticide. Accumulation of these pesticides in bodies of fishes, birds, mammals and man affects nervous system, fertility and causes thinning of egg shells in birds.

Bacteria, Viruses and Parasites - These are sourced from human and animal excreta, they are infectious agents.

Plastics, Detergents, Oil and Gasoline - They are a waste from industries, household and farms. They trigger organic pollution and is harmful to health.

Inorganic Chemicals - Inorganic chemicals like acids, salts, metals are a result of industrial effluents, household cleansers, and surface run-off and are injurious to health.

Radioactive Materials - Mining and ores processing, power plants, weapons production and natural give rise to radioactive pollution like that of uranium, thorium, cesium, iodine and radon. Radioactive pollution causes serious health diseases to all organisms.

Sediments - Sedimentation of soil, silt due to land erosion and deposition causes disruption in ecosystem.

Plant Nutrients - Nutrients like nitrates, phosphates, and ammonium are let off from agricultural and urban fertilizers, sewage and manure. Excess of nutrients cause eutrophication and affect the ecosystem.

Animal Manure and Plant Residues - These substances in water causes increased algal blooms and microorganism population. This increases oxygen demand of water, affecting aquatic ecosystem. This is introduced into water due to sewage, agricultural run-off, paper mills, food processing etc.

Thermal Pollution - Temperature changes of water caused due to using water as cooling agent in power plants and industries causes increase in water temperature affecting the aquatic life.

Parameters to Monitor Septic System Performance

There are many characteristics to monitor an on-site wastewater treatment system’s performance. They vary from something as simple as checking for sewage on the surface, to complicated laboratory analysis.

Biochemical Oxygen Demand (BOD5) is the most widely used parameter applied to wastewater. It is a measurement of the dissolved oxygen used by microorganisms in the oxidation of organic matter in sewage in five days.

Color is an indication of how ‘clean’ the wastewater is. A black sample represents wastewater that is anaerobic and still need significant treatment. A clear sample represents a sample where the BOD5 and TSS have been minimized. The amount of fecal coliform cannot be estimated with a visual inspection.

Dissolved Oxygen (DO) is a measure to determine how much oxygen is in wastewater. Septic tanks usually have very low values of DO because the microorganisms in the septic tank use up all oxygen initially present. A typical value for DO in a septic tank is less than 1 mg/L.

Fecal Coliform is an indicator organism. There are many pathogenic organisms present in wastewater. They are difficult to isolate and identify.

Fats, Oils and Grease (FOG) are added to wastewater through the use of butter, lard, margarine, vegetable oil, and meat. A typical value for FOG from a septic tank is 10 — 50 mg/L.

Nitrogen is a nutrient essential to the growth of plants and microorganisms and in high levels can be toxic to humans. Wastewater naturally contains fairly high levels of nitrogen, typically in the range of 50-90 mgN/L. It is found in four different forms: organic nitrogen, ammonia, nitrite and nitrate.

Phosphorus is a nutrient essential to the growth of plants and microorganisms. This nutrient may cause increased growth of aquatic vegetation and algae in surface waters that can result in eutrophication impacts. A typical value for septic tank effluent is 7- 20 mg/L of phosphorus.

Total Suspended Solids (TSS) is a measure of the organic and inorganic solids, which remain in wastewater after separation occurs in the septic tank. Typical suspended solids values of septic tank effluent range from 20-140 mg/L.

Temperature of wastewater is a very important parameter because of its effect on chemical reactions. Temperature of wastewater varies from 45-70 ° F depending on the season.

Turbidity is a measure of the light-transmitting properties of water. It is another test to easily measure the quality of waste with respect to suspended matter.

Odor is often detected when a system is not performing properly. A properly functioning system will have little or no odor.

Flow Meters are used to measure the volume of wastewater going to an on-site system. They are usually located in the basement.

The Importance of Wastewater Treatment

Across the world, there continues to be huge volumes of wastewater pumped directly into rivers, streams and the ocean itself. The impact of this is severe – aside from the damage to the marine environment and to fisheries it can cause, it does little to preserve water at a time when many are predicting that a global shortage is just around the corner.

As it stands this method of disposing of wastewater – any form of water that has been contaminated by a commercial or domestic process, including sewage and byproducts of manufacturing and mining – is largely an issue in developing nations

Waste is not something that should be discarded or disposed of with no regard for future use. It can be a valuable resource if addressed correctly, through policy and practice. With rational and consistent waste management practices there is an opportunity to reap a range of benefits. Those benefits include:

Economic - Improving economic efficiency through the means of resource use, treatment and disposal and creating markets for recycles can lead to efficient practices in the production and consumption of products and materials resulting in valuable materials being recovered for reuse and the potential for new jobs and new business opportunities.
Social - By reducing adverse impacts on health by proper waste management practices, the resulting consequences are more appealing settlements. Better social advantages can lead to new sources of employment and potentially lifting communities out of poverty especially in some of the developing poorer countries and cities.
Environmental - Reducing or eliminating adverse impacts on the environmental through reducing, reusing and recycling, and minimizing resource extraction can provide improved air and water quality and help in the reduction of greenhouse emissions.
Inter-generational Equity - Following effective waste management practices can provide subsequent generations a more robust economy, a fairer and more inclusive society and a cleaner environment

Wastewater Treatment

Wastewater treatment refers to the process of removing pollutants from water previously employed for industrial, agricultural, or municipal uses. The techniques used to remove the pollutants present in wastewater can be broken into biological, chemical, physical and energetic. These different techniques are applied through the many stages of wastewater treatment.

Primary Treatment

Screening is the first technique employed in primary treatment, which is the first step in the wastewater treatment process.

This step removes all sorts of refuse that has arrived with the wastewater such as plastic, branches, rags, and metals. The screening process is used primarily to present the clogging and interference of the following wastewater treatment processes.

In order to remove coarse solids, numerous types of detritus tanks, grinders, and cyclonic inertial separation are utilized, including a comminutor and a grit chamber.

A comminutor, also known as the grinding pump, houses a rotating cutting screen. This cutting screen shreds any large chunks of organic matter in the wastewater into smaller pieces.

A grit chamber allows pieces of rock, metal, bone, and even egg shells, which are denser than organic materials, to settle out of the waste stream.

The last step in primary treatment is sedimentation, which occurs in the primary clarifier.

Sedimentation simply entails the physical settling of matter, due to its density, buoyancy, and the force of gravity. Certain chemicals known as coagulants and flocculants are often used to expedite this process by encouraging aggregation of particles. Through sedimentation, the larger solids are removed in order to facilitate the efficiency of the following procedures and also to reduce the biological oxygen demand of the water.

Secondary Treatment

Once the wastewater leaves the primary treatment steps, it enters secondary treatment. The primary effluent is then transferred to the biological or secondary stage. The first step in the secondary treatment process is the aeration tank. Here, the wastewater is mixed with a controlled population of bacteria and an ample supply of oxygen. The microorganisms digest the fine suspended and soluble organic materials, thereby removing them from the wastewater.

The wastewater is then passed through a secondary clarifier, which performs sedimentation. The effluent is then transferred to secondary clarifiers, where the biological solids or sludges are settled by gravity. As with the primary clarifier, these sludges are pumped to anaerobic digesters, and the clear secondary effluent may flow directly to the receiving environment or to a disinfection facity prior to release.

The disinfection of wastewater through the sue of chemicals such as chlorine typically acts as the final step in wastewater treatment. Disinfection seeks to remove harmful organics and pathogens causing cholera, polio, typhoid, hepatitis, and a number of other bacterial, viral, and parasitic diseases from the water.

There are several variations of secondary treatment, including:

activated sludge
trickling filtration
rotating biological contactors (RBC)
lagoons and ponds

Tertiary Treatment

Tertiary, or advanced, wastewater treatment is the term applied to additonal treatment that is needed to remove suspended and dissolved substances remaining after conventional secondary treatment. This may be accomplished using a variety of physical, chemical, or biological treatment processes to remove the targeted pollutants. Advanced treatment may be used to remove such things as color, metals, organic chemicals, and nutrients such as phosphorus and nitrogen.

Biological waste treatment

Biological treatment methods use microorganisms, mostly bacteria, in the biochemical decomposition of wastewaters to stable end products. More microorganisms, or sludges, are formed and a portion of the waste is converted to carbon dioxide, water and other end products. Generally, biological treatment methods can be divided into aerobic and anaerobic methods, based on availability of dissolved oxygen.

The purpose of wastewater treatment is generally to remove from the wastewater enough solids to permit the remainder to be discharged to a receiving water without interfering with its best or proper use. The solids which are removed are primarily organic but may also include inorganic solids. Treatment must also be provided for the solids and liquids which are removed as sludge. Finally, treatment to control odors, to retard biological activity, or destroy pathogenic organisms may also be needed.

Secondary treatment depends primarily upon aerobic organisms which biochemically decompose the organic solids to inorganic or stable organic solids. It is comparable to the zone of recovery in the self-purification of a stream.

The devices used in secondary treatment may be divided as follows:

                                                             Biological

Aerobic                                                                                  Anaerobic
Activated Sludge Treatment                                         Anaerobic Digestion
Trickling Filtration                                                              Septic Tanks
Oxidation Ponds                                                                     Lagoons
Lagoons
Aerobic Digestion
RBC

Dairy Wastewater Treatment System

The dairy industry involves processing raw milk into products including milk, butter, cheese, yogurt, using processes such as chilling, pasteurization, and homogenization. Typical by-products include buttermilk, whey, and their derivatives.
Huge amounts of water are used during the process producing effluents containing dissolved sugars and proteins, fats, and possibly residues of additives. These effluents have the following characteristics

· Biochemical oxygen demand (BOD), with an average ranging from 0.8 to 2.5 kilograms per metric ton (kg/t) of milk in the untreated effluent

· Chemical oxygen demand (COD), which is normally about 1.5 times the BOD level

· Total suspended solids (TSS), at 100–1,000 milligrams per liter (mg/l)

· Total dissolved solids (TDS): phosphorus (10–100 mg/l), and nitrogen (about 6% of the BOD level).

Benefits:

· Optimization of use of water and cleaning chemicals with option for recirculation of cooling waters.

· Segregation of effluents from sanitary installations, processing, and cooling (including condensation) systems; this would facilitate ability to recycle the wastewater.

· Energy recovery through use of heat exchangers for cooling and condensing.

· Use of high-pressure nozzles to minimize water usage.

Dairy wastewater is treated by adjusting pH and using strong coagulant chemistry to break any emulsions caused by cleaning agents and sanitizers and to precipitate solids and fats. The chemicals are added to cause de-emulsification, precipitation, coagulation, and flocculation.

The typical method to treat Dairy Processing wastewater is as follows:

Stage 1 Emulsion Cracking/pH Adjustment/Precipitation and Coagulation:
pH is raised (or lowered) to ~8.5 with the pH controller using caustic (or acid). A coagulant de-emulsifier is added to break any emulsion and cause precipitation of the solids. A “pin floc” is developed indicating the emulsion and the suspended solids are precipitated.

Stage 2 - Flash Mix:
The wastewater with it’s precipitated pin floc is introduced to the flash mix zone where a polymer flocculent is added. This stage maximizes flocculent dispersion throughout the coagulated wastewater.

Stage 3 - Flocculation:
The wastewater is now introduced to the slow mix zone to agglomerate the floc into larger particles suitable to be enmeshed with the air bubbles.

Clarifier, Dissolved Air Flotation (DAF):
The flocculated wastewater is introduced into the DAF inlet where the floc particles are comingled with a pressurized dissolved fine bubble recycle stream. The floc particles attach to the bubbles and float to the surface where they are mechanically skimmed into the float scum sludge chamber. The clarified treated water then exits the end of the DAF and flows downstream to sewer or further treatment if necessary.

DAF Sludge Handling:
The resulting DAF waste scum/sludge is removed from the DAF automatically as the scum accumulates and is pumped to the sludge holding tank where it further thickens and accumulates a batch for disposal or processing in a filter press. The sludge is mixed and conditioned with a filter aid such as DE to improve porosity and filterability which will improve cake dryness and prevent premature blinding of the filter cloths.

Sludge Dewatering:
The thickened DAF scum/sludge is allowed to accumulate sufficiently to provide a full batch for the Filter Press. The filter press is pumped with the sludge until it is full. The filter press is then emptied of the “cake” which is a semi solid of approximately 20-35 % solids. Sludge cake is high in solids and should be disposed of according to environmental regulations.

APPLICATIONS:

· Dairy products companies

· Solid cheese

· Cream cheese

· Sour cream and cottage cheese

· Dry milk

· Sweetened condensed milk

· Ice cream.

Bioremediation

Bioremediation is a treatment process that uses naturally occurring microorganisms (yeast, fungi, or bacteria) to break down, or degrade, hazardous substances into less toxic or nontoxic substances. Microorganisms, just like humans, eat and digest organic substances for nutrients and energy. In chemical terms, "organic" compounds are those that contain carbon and hydrogen atoms. Certain microorganisms can digest organic substances such as fuels or solvents that are hazardous to humans. The microorganisms break down the organic contaminants into harmless products -- mainly carbon dioxide and water (Figure 1). Once the contaminants are degraded, the microorganism population is reduced because they have used all of their food source. Dead microorganisms or small populations in the absence of food pose no contamination risk.

2. How does it work?

Microorganisms must be active and healthy in order for bioremediation to take place. Bioremediation technologies assist microorganisms' growth and increase microbial populations by creating optimum environmental conditions for them to detoxify the maximum amount of contaminants. The specific bioremediation technology used is determined by several factors, for instance, the type of microorganisms present, the site conditions, and the quantity and toxicity of contaminant chemicals. Different microorganisms degrade different types of compounds and survive under different conditions.

Bioremediation can take place under aerobic and anaerobic conditions. In aerobic conditions, microorganisms use available atmospheric oxygen in order to function. With sufficient oxygen, microorganisms will convert many organic contaminants to carbon dioxide and water. Anaerobic conditions support biological activity in which no oxygen is present so the microorganisms break down chemical compounds in the soil to release the energy they need. Sometimes, during aerobic and anaerobic processes of breaking down the original contaminants, intermediate products that are less, equally, or more toxic than the original contaminants are created.

Types of bioremediation:-
Bioremediation has three types and all the types are used to remove contamination from the toxic site or from rivers.

Intrinsic Bioremediation:-
This process of bioremediation is also called as natural attenuation. It occurs in the soils and water which are contaminated with toxins. Microorganisms are involved in this type of bioremediation.

Biostimultion:-
In this type of bioremediation, environment is modified by motivating the bacteria used for bioremediation. The experts release oxygen and other nutrients in the soil in which microorganisms are residing.

Bioaugmentation:-
Sometimes microorganisms are needed to remove particular contaminants from the soil or water. Municipal waste water facilities use this type of bioremediation

Role of Biotechnology in Bioremediation:-
Biotechnology plays a vital role in the process of bioremediation because it provides natural mechanisms for the removal of contaminants from the environment, from water and soil. Biotechnology mechanisms are applied to bioremediation when the contaminants are composed if industrial wastes. Scientists are making efforts to produce microorganisms through genetic engineering techniques which will have higher metabolic activities and will be able to digest chemicals more efficiently. In situ developments in the bioremediation processes are possibly less in cost and they do not effect the environment in a negative way.

Advantages

There are a number of cost/efficiency advantages to bioremediation, which can be employed in areas that are inaccessible without excavation. For example, hydrocarbon spills (specifically, petrol spills) or certain chlorinated solvents may contaminate groundwater, and introducing the appropriate electron acceptor or electron donor amendment, as appropriate, may significantly reduce contaminant concentrations after a long time allowing for acclimation. This is typically much less expensive than excavation followed by disposal elsewhere, incineration or other ex situ treatment strategies, and reduces or eliminates the need for "pump and treat", a practice common at sites where hydrocarbons have contaminated clean groundwater.

Phytoremediation

Phytoremediation (from Ancient Greek φυτο (phyto), meaning "plant", and Latin remedium, meaning "restoring balance") describes the treatment of environmental problems (bioremediation) through the use of plants that mitigate the environmental problem without the need to excavate the contaminant material and dispose of it elsewhere.

Phytoremediation consists of mitigating pollutant concentrations in contaminated soils, water, or air, with plants able to contain, degrade, or eliminate metals, pesticides, solvents, explosives, crude oil and its derivatives, and various other contaminants from the media that contain them.

Application

Phytoremediation may be applied wherever the soil or static water environment has become polluted or is suffering ongoing chronic pollution. Examples where phytoremediation has been used successfully include the restoration of abandoned metal mine workings, reducing the impact of contaminants in soils, water, or air. Contaminants such as metals, pesticides, solvents, explosives,^[1] and crude oil and its derivatives, have been mitigated in phytoremediation projects worldwide. Many plants such as mustard plants, alpine pennycress, hemp, and pigweed have proven to be successful at hyperaccumulating contaminants at toxic waste sites.

Over the past 20 years, this technology has become increasingly popular and has been employed at sites with soils contaminated with lead, uranium, and arsenic. While it has the advantage that environmental concerns may be treated in situ; one major disadvantage of phytoremediation is that it requires a long-term commitment, as the process is dependent on a plant's ability to grow and thrive in an environment that is not ideal for normal plant growth. Phytoremediation may be applied wherever the soil or static water environment has become polluted or is suffering ongoing chronic pollution. Examples where phytoremediation has been used successfully include the restoration of abandoned metal-mine workings, reducing the impact of sites where polychlorinated biphenyls have been dumped during manufacture and mitigation of ongoing coal mine discharges.

Phytoremediation refers to the natural ability of certain plants called hyperaccumulators to bioaccumulate, degrade,or render harmless contaminants in soils, water, or air.

Advantages and limitations

Advantages:

the cost of the phytoremediation is lower than that of traditional processes both in situ and ex situ
the plants can be easily monitored
the possibility of the recovery and re-use of valuable metals (by companies specializing in “phyto mining”)
it is potentially the least harmful method because it uses naturally occurring organisms and preserves the environment in a more natural state.

Limitations:

phytoremediation is limited to the surface area and depth occupied by the roots.
slow growth and low biomass require a long-term commitment
with plant-based systems of remediation, it is not possible to completely prevent the leaching of contaminants into the groundwater (without the complete removal of the contaminated ground, which in itself does not resolve the problem of contamination)
the survival of the plants is affected by the toxicity of the contaminated land and the general condition of the soil.
bio-accumulation of contaminants, especially metals, into the plants which then pass into the food chain, from primary level consumers upwards or requires the safe disposal of the affected plant material.

Xenobiotics

Man made chemicals present in the nature at high concentrations polluting the environment is known as Xenobiotic compounds. These compounds are not commonly produced by nature. Some microbes have been seen to be capable of breaking down of xenobiotics to some extent. But most of the xenobiotic compounds are non degradable in nature. Such compounds are known to be recalcitrant in nature.

The properties of xenobiotic compounds attributing to its recalcitrant properties are:

(i) Non recognizable as substrate by microbes to act upon and degrade it.
(ii) It does not contain permease which is needed for transport into microbial cell.
(iii) Large molecular nature makes it difficult to enter microbial cell.
(iv) They are highly stable and insolubility to water adds to this property.
(v) Mostly toxic in nature.

The recalcitrant xenobiotic compounds can be divided into different groups depending on their chemical composition

Halocarbons: They consist of halogen group in their structure. Mainly used in solvents, pesticides, propellants etc. They are highly volatile and escape into nature leading to destruction of ozone layer of atmosphere. The compounds present in insecticides, pesticides etc,. leach into soil where they accumulate and result in biomagnification.
Polychlorinated biphenyls (PCBs): They consist of a halogen group and benzene ring. They are mainly used in plasticisers, insulator coolants in transformers etc. They are chemically and biologically inert adding on to its recalcitrant nature.

Synthetic polymers: These are mainly used to form plastics like polyester, polyvinyl chloride etc. They are insoluble in water and of high molecular weight explaining the recalcitrant property.

Alkylbenzyl Sulphonates: They consist of a sulphonate group which resists break down by microbes. They are mostly found in detergents.

Oil mixtures: When oil spills occur covering a huge area the break down by action of microbes becomes non effective. They become recalcitrant as they are insoluble in water and some components of certain oils are toxic in higher concentrations.

Common PhACs found in the environment

Analgesics (anti-inflammatory and antipyretic)

Antibiotics

Biochemical Oxygen Demand (BOD)

Biochemical Oxygen Demand, BOD, as it is commonly abbreviated, is one of the most important and useful parameters (measured characteristics) indicating the organic strength of a wastewater. BOD measurement permits an estimate of the waste strength in terms of the amount of dissolved oxygen required to break down the wastewater. The BOD test is one of the most basic tests used in the wastewater field. It is essentially a measure of the biological and the chemical component of the waste in terms of the dissolved oxygen needed by the natural aerobic biological systems in the wastewater to break down the waste under defined conditions. Generally the BOD test is carried out by determining the dissolved oxygen on the wastewater or a diluted mixture at the beginning of the test period, incubating the wastewater mixture at 20°C, and determining the dissolved oxygen at the end of 5 days. The difference in dissolved oxygen between the initial measurement and the fifth day measurement represents the biochemical oxygen demand.

While BOD describes the biological oxidation capacity of a wastewater, it is not a measure of the total potential oxidation of the organic compounds present in the wastewater. A number of chemical tests are used to measure this parameter, either in terms of the oxygen required for virtually complete oxidation, or in terms of the element carbon. Probably the most common test for estimating industrial wastewater strength is the Chemical Oxygen Demand (COD) Test. This test essentially measures the chemical oxidation of the wastewater by a strong oxidizing agent in an acid solution. The value for the COD test is always greater than the BOD test and is not always a good indication of BOD values for the same waste.

A test which measures carbon and which is being used to a greater extent in measuring wastewater strength is the TOC (Total Organic Carbon) test where the carbon is oxidized by catalytic combustion to carbon dioxide and the carbon dioxide is measured.

Test Limitations[edit]

The test method involves variables limiting reproducibility. Tests normally show observations varying plus or minus ten to twenty percent around the mean.^[14]:82

Toxicity[edit]

Some wastes contain chemicals capable of suppressing microbiological growth or activity. Potential sources include industrial wastes, antibiotics in pharmaceutical or medical wastes, sanitizers in food processing or commercial cleaning facilities, chlorination disinfection used following conventional sewage treatment, and odor-control formulations used in sanitary waste holding tanks in passenger vehicles or portable toilets. Suppression of the microbial community oxidizing the waste will lower the test result.^[14]:85

Appropriate Microbial Population[edit]

The test relies upon a microbial ecosystem with enzymes capable of oxidizing the available organic material. Some waste waters, such as those from biological secondary sewage treatment, will already contain a large population of microorganisms acclimated to the water being tested. An appreciable portion of the waste may be utilized during the holding period prior to commencement of the test procedure. On the other hand, organic wastes from industrial sources may require specialized enzymes. Microbial populations from standard seed sources may take some time to produce those enzymes. A specialized seed culture may be appropriate to reflect conditions of an evolved ecosystem in the receiving waters.

Chemical Oxygen Demand (COD)

The Chemical Oxygen Demand (COD) test measures the oxygen equivalent consumed by organic matter in a sample during strong chemical oxidation. The strong chemical oxidation conditions are provided by the reagents used in the analysis. Potassium dichromate is used as the oxygen source with concentrated sulfuric acid added to yield a strong acid medium. Several reagents are added during the set up of the analysis to drive the oxidation reaction to completion and also to remove any possible interferences. Specifically, these reagents are mercuric sulfate, silver sulfate and sulfamic acid. Mercuric sulfate is added to remove complex chloride ions present in the sample. Without the mercuric sulfate the chloride ions would form chlorine compounds in the strong acid media used in the procedure. These chlorine compounds would oxidize the organic matter in the sample, resulting in a COD value lower than the actual value. Silver sulfate is added as a catalyst for the oxidation of short, straight chain organics and alcohols. Again, without the silver sulfate the COD of the sample would be lower than the actual value. Sulfamic acid is added to remove interferences caused by nitrite ions. Without sulfamic acid the COD of the sample would measure higher than the actual value.

Even with the use of these additional reagents the oxidation of the organic matter is not always 100% complete. Volatile organics, ammonia and aromatic hydrocarbon are not oxidized to any great degree during the procedure.

The advantages of the COD test as compared to the BOD test are:

COD results are available much sooner.
The COD test requires fewer manipulations of the sample.
The COD test oxidizes a wider range of chemical compounds.
It can be standardized more easily.

The major disadvantage of the COD test is that the results are not directly applicable to the 5-day BOD results without correlation studies over a long period of time. The samples used for the COD analysis may be grab or composite. Preservation of the sample can be accomplished by adding sulfuric acid to depress the pH to 2 and the holding time with preservation is 7 days.

Total Organic Carbon (TOC)

Total Organic Carbon (TOC) is a sum measure of the concentration of all organic carbon atoms covalently bonded in the organic molecules of a given sample of water. TOC is typically measured in Parts Per Million (ppm or mg/L), although some industries require more refined measurements expressed in parts per Parts Per Billion (ppb or µg/L), or even Parts Per Trillion (ppt).

As a sum measurement, Total Organic Carbon does not identify specific organic contaminants. It will, however, detect the presence of all carbon-bearing molecules, thus identifying the presence of any organic contaminants, regardless of molecular make-up.

A typical analysis for TOC measures both the Total Carbon (TC) as well as Inorganic Carbon (IC, or carbonate). Subtracting the Inorganic Carbon from the Total Carbon yields TOC. (TC-IC=TOC). Another common variant of TOC analysis involves removing the inorganic carbon by purging the acidified sample with carbon-free air prior to measurement, then measuring the remaining carbon. This measurement is more accurately called non-purgeable organic carbon (NPOC).

Who Measures TOC?

Total Organic Carbon is a broadly useful measurement. TOC is a required measurement in municipal water and wastewater systems, and is also a valuable measurement in a host of industries that rely on TOC analysis for process control and for reporting of regulated organic discharge levels. Industry often turns to TOC analysis to protect vital systems by monitoring raw water feedstock and process water quality.

IN MUNICIPAL DRINKING WATER:

As a regulated monitoring parameter in municipal and environmental water programs, TOC measurement provides a method of detecting organic contaminants that can pose a threat to public health.

IN MUNICIPAL WASTEWATER:

Early detection of high organic loads in influent enable plant operators to optimize processing for improved system efficiency. Analyzing TOC levels in effluent demonstrates compliant levels of organics prior to discharging treated wastewater to surface waters.

IN INDUSTRIAL WASTEWATER:

Industrial discharge is carefully regulated, and excessive organics in industrial wastewater can result in fines, citations and, in extreme cases, even plant closure. Individual states enforce national US EPA regulations by requiring that industries hold discharge permits in order to operate. National Pollutant Discharge Elimination System (NPDES) permits stipulate each permit holder's unique limits and monitoring requirements for discharge of contaminants.

IN PROCESS INDUSTRIES:

In process industries TOC analysis provides cleaning validation and detects organic contaminants in process water. The presence of organic material in pure water systems can indicate a failure in filtration systems, storage methods, compromised seals or other system component failure. Monitoring total organic carbon is vital in many industries, including Power Generation, Production of Pharmaceuticals, Semiconductor Manufacturing, and any industry where ultrapure water (De-Ionized, or DI Water) is produced or consumed.

How Is TOC Measured?

TOC measurement is achieved by oxidizing a sample of water, thus converting the organic constituents to carbon dioxide (CO2). Oxidation is achieved through combustion, or with a UV/persulfate reactor. If Inorganic carbon can be stripped out through acidification and the resulting CO2 is then measured with a nondispersive infrared detector. Organic molecules can be oxidized using heat, oxygen, ultraviolet irradiation, chemical oxidants, or combinations of these.

Sulphur Cycle

Sulphur is an important component of most proteins, few vitamins and enzymes.

Though sulphur occurs in gaseous form, as hydrogen sulphide (H₂S) and sulphur dioxide (SO₂), the residence time of sulphur in atmosphere is very small (about 4 x 10¹⁰ kg) and its main reservoir pool is the soil (contains about 4 x 10¹⁸ kg in the form of sulphates, sulphides and organic sulphur).

So, sulphur cycle is classified under sedimentary cycles.

Steps of Sulfur Cycle

The following steps are involved in the process of sulfur cycle and they are of ecological importance

1) Conversion of inorganic hydrogen sulfide to organic sulfur form

2) Sulfide oxidation to sulfate

3) Reduction of sulfate to sulfide

4) Encapsulation of sulfur compounds and incorporation into organic sulfur form.

Research has proven that sulfur can be reduced in biological and thermodynamic states where in sulfate reduction can involve

Microbial process for conversion of sulfate to sulfide with gain of energy
Forward and reverse pathways which lead from the uptake and liberation of sulfate by cell and it’s inter conversion to various sulfur compounds which are intermediates.

Sources of Sulphur

a) Soil, water and rocks containing sulphates, sulphides and organic sulphur, and also body of living organisms.

b) Oxides of sulphur in the atmosphere due to the burning of fossil fuels and volcanic emissions.

c) Sulphur occurs as elemental sulphur also.

Sulphur Utilisation

i) Green plants (producers) require sulphur in the form of sulphates (SO₄^-2), which they absorb from soil and incorporate sulphur in their proteins.

ii) Animals take in sulphur from plants as food through food chain and few animals can get from water also.

Sulphur Production

1) Decomposers like Aspergillus (aerobic fungi), Neurospora (aerobic fungi) and Escherichia (anaerobic bacteria) act on the dead and decaying organic matter of plants and animals, releasing hydrogen sulphide (H₂S) to the environment.

2) Heterotrophic bacteria like Desulfavibrio and Acetobacter reduce sulphates to elemental sulphur or sulphides under anaerobic conditions. Though sulphides are harmful to most organisms, sulphur bacteria oxidise them to sulphate and bring back the element to cycle.

3) Oxides of sulphur (SO₂ and H₂S) in the atmosphere, gets dissolved in rain water and return to soil as sulphates and sulphuric acid.

4) From the reservoir pool in deep sediments in the sea, sulphur reaches the land through food chains, sea sprays and geological upheavals.

5) Hydrogen sulphide is released into atmosphere from lakes, marshes and water logged soils, which is oxidised to sulphur dioxide in the atmosphere.

Atmospheric Inversion (meteorology)

In meteorology, an inversion is a deviation from the normal change of an atmospheric property with altitude. It almost always refers to a temperature inversion, i.e., an increase in temperature with height, or to the layer (inversion layer) within which such an increase occurs.^[1]

An inversion can lead to pollution such as smog being trapped close to the ground, with possible adverse effects on health. An inversion can also suppress convection by acting as a "cap". If this cap is broken for any of several reasons, convection of any moisture present can then erupt into violent thunderstorms. Temperature inversion can notoriously result in freezing rain in cold climates.

Normal atmospheric conditions

Usually, within the lower atmosphere (the troposphere) the air near the surface of the Earth is warmer than the air above it, largely because the atmosphere is heated from below as solar radiation warms the Earth's surface, which in turn then warms the layer of the atmosphere directly above it e.g. by thermals (convective heat transfer).

How and why inversions occur

Under certain conditions, the normal vertical temperature gradient is inverted such that the air is colder near the surface of the Earth. This can occur when, for example, a warmer, less dense air mass moves over a cooler, denser air mass. This type of inversion occurs in the vicinity of warm fronts, and also in areas of oceanic upwelling such as along the California coast. With sufficient humidity in the cooler layer, fog is typically present below the inversion cap. An inversion is also produced whenever radiation from the surface of the earth exceeds the amount of radiation received from the sun, which commonly occurs at night, or during the winter when the angle of the sun is very low in the sky. This effect is virtually confined to land regions as the ocean retains heat far longer. In the polar regions during winter, inversions are nearly always present over land.

A warmer air mass moving over a cooler one can "shut off" any convection which may be present in the cooler air mass. This is known as a capping inversion. However, if this cap is broken, either by extreme convection overcoming the cap, or by the lifting effect of a front or a mountain range, the sudden release of bottled-up convective energy — like the bursting of a balloon — can result in severe thunderstorms. Such capping inversions typically precede the development of tornadoes in the midwestern United States. In this instance, the "cooler" layer is actually quite warm, but is still denser and usually cooler than the lower part of the inversion layer capping it.

Consequences

Temperature inversion stops atmospheric convection (which is normally present) from happening in the affected area and can lead to the air becoming stiller and murky from the collection of dust and pollutants that are no longer able to be lifted from the surface. This can become a problem in cities where many pollutants exist.

Inversion effects occur frequently in big cities such as:

Methanogenesis

Methanogenesis is a form of anaerobic respiration that uses carbon as a electron acceptor and results in the production of methane.

Methanogenesis or biomethanation is the formation of methane by microbes known as methanogens. The production of methane is an important and widespread form of microbial metabolism. In most environments, it is the final step in the decomposition of biomass.

The decomposition of biowaste occurs in four stages: hydrolysis, acidogenesis, acetogenesis and methanogenesis.

Hydrolysis

During hydrolysis, the first stage, bacteria transform the particulate organic substrate into liquefied monomers and polymers i.e. proteins, carbohydrates and fats are transformed to amino acids, monosaccharides and fatty acids respectively. Equation 2.13 shows an example of a hydrolysis reaction where organic waste is broken down into a simple sugar, in this case, glucose (Ostrem, 2004).

Equation 1: C₆H₁₀O₄ + 2H₂O → C₆H₁₂O₆ + 2H₂

Acidogenesis

In the second stage, acidogenic bacteria transform the products of the first reaction into short chain volatile acids, ketones, alcohols, hydrogen and carbon dioxide. The principal acidogenesis stage products are propionic acid (CH₃CH₂COOH), butyric acid (CH₃CH₂CH₂COOH), acetic acid (CH₃COOH), formic acid (HCOOH), lactic acid (C₃H₆O₃), ethanol (C₂H₅OH) and methanol (CH₃OH), among other. From these products, the hydrogen, carbon dioxide and acetic acid will skip the third stage, acetogenesis, and be utilized directly by the methanogenic bacteria in the final stage (Figure 2). Equations 2, 3 (Ostrem, 2004) and 4 (Bilitewski et al., 1997) represent three typical acidogenesis reactions where glucose is converted to ethanol, propionate and acetic acid, respectively.

Equation 2: C₆H₁₂O₆ ↔ 2CH₃CH₂OH + 2CO₂

Equation 3: C₆H₁₂O₆ + 2H₂ ↔ 2CH₃CH₂COOH + 2H₂O

Equation 4: C₆H₁₂O₆ → 3CH₃COOH

Acetogenesis

In the third stage, known as acetogenesis, the rest of the acidogenesis products, i.e. the propionic acid, butyric acid and alcohols are transformed by acetogenic bacteria into hydrogen, carbon dioxide and acetic acid (Figure 2). Hydrogen plays an important intermediary role in this process, as the reaction will only occur if the hydrogen partial pressure is low enough to thermodynamically allow the conversion of all the acids. Such lowering of the partial pressure is carried out by hydrogen scavenging bacteria, thus the hydrogen concentration of a digester is an indicator of its health (Mata-Alvarez, 2003). Equation 5 represents the conversion of propionate to acetate, only achievable at low hydrogen pressure. Glucose (Equation 6) and ethanol (Equation 7) among others are also converted to acetate during the third stage of anaerobic fermentation (Ostrem, 2004).

Equation 5: CH₃CH₂COO^- + 3H₂O ↔ CH₃COO^- + H⁺ + HCO₃^- + 3H₂

Equation 6: C₆H₁₂O₆ + 2H₂O ↔ 2CH₃COOH + 2CO₂ + 4H₂

Equation 7: CH₃CH₂OH + 2H₂O ↔ CH₃COO^- + 2H₂ +H⁺

Methanogenesis

The fourth and final stage is called methanogenesis. During this stage, microorganisms convert the hydrogen and acetic acid formed by the acid formers to methane gas and carbon dioxide (Equations 2.20, 2.21 and 2.22) (Verma, 2002). The bacteria responsible for this conversion are called methanogens and are strict anaerobes. Waste stabilization is accomplished when methane gas and carbon dioxide are produced.

Equation 8: CO₂ + 4H₂ → CH₄ + 2H₂O

Equation 9: 2C₂H₅OH + CO₂ → CH₄ + 2CH₃COOH

Equation 10: CH₃COOH → CH₄ + CO₂

Applications and Benefits of Environmental Biotechnology

Environmental Biotechnology enables us to harness biological processes commercially and that too in an Eco-friendly manner. The emphasis lies on making use of biological systems and reusing natural wastes.

What is Environmental Biotechnology?

Biotechnology applications in food security, agriculture, climate change, and climate mitigation are well known. The industrial applications of biotechnology are a profitable option for food and agriculture businesses. Moreover, these processes ensure that minimal damage is inflicted upon our environment.

Significance towards agriculture, food security, climate change mitigation and adaptation and the MDGs[edit]

Science through the IAASTD has called for the advancement of small-scale agro-ecological farming systems and technology in order to achieve food security, climate change mitigation, climate change adaptation and the realisation of the Millennium Development Goals. Environmental biotechnology has been shown to play a significant roll in agroecology in the form of zero waste agriculture and most significantly through the operation of over 15 million biogas digesters worldwide.

Significance towards industrial biotechnology[edit]

Consider an environment in which pollution of a particular type is maximum. Let us consider the effluents of a starch industry which has mixed up with a local water body like a lake or pond. We find huge deposits of starch which are not so easily taken up for degradation by micro-organisms except for a few exemptions. we isolate a few micro-organisms from the polluted site and scan for any significant changes in their genome like mutations or evolutions. The modified genes are then identified. This is done because, the isolate would have adapted itself to degrade/utilize the starch better than other microbes of the same genus. Thus, the resultant genes are cloned onto industrially significant micro-organisms and are used for more economically significant processess like in pharmaceutical industry, fermentations...etc.

Similar situations can be elucitated like in the case of oil spills in the oceans which require cleanup, microbes isolated from oil rich environments like oil wells, oil transfer pipelines...etc. have been found having the potential to degrade oil or use it as an energy source. Thus they serve as a remedy to oil spills.

Still another elucidation would be in the case of microbes isolated from pesticide rich soils These would be capable of utilizing the pesticides as energy source and hence when mixed along with bio-fertilizers, would serve as excellent insurance against increased pesticide-toxicity levels in agricultural platform.

Applications of Environmental Biotechnology

Environmental biotechnology finds use in various fields and industries. In this section we have listed certain most popular and commonly practiced applications of environmental biotechnology around us.

Bio-composting involves combining organic materials under certain controlled conditions that decomposes them at a faster rate than they would decompose under natural conditions in free surroundings.
Bioenergy – We hear about fuels like biogas, biomass, and hydrogen being used for industrial, domestic, and space exploration purposes. All these fuels belong to the category of Bioenergy. Of late, need of the hour has become finding alternate resources of energy that are clean and equally efficient. Energy generation from organic waste or biomass is the finest example of green energy. These are all ecofriendly solutions to our pollution woes. Biomass energy supply demand balances have become a component of energy sector analysis and planning and assumed greater importance in countries.
Bioremediation is a clean-up technology that uses naturally occurring microorganisms to degrade hazardous substances into less toxic or nontoxic compounds.
Bio-Transformation is a process of Biological changes of complex compound to simpler toxic to non-toxic or vice-versa. It is used in manufacturing industries where toxic substances are released as bi-products.
Biomarker is a biological response to a chemical that gives a measure of exposure and, of toxic effect. Biological markers can provide molecular evidence of the correlation among oils and their sources.

Nitrogen Removal

High levels of nitrogen in water resources create hazard to human health and the environment. In many watersheds nitrogen from wastewater contributes 40 to 80 percent of total nitrogen loads (Lombardo, 2007). When Designing wastewater treatment system, nitrogen removal is the main concern. There are different methods used to remove nitrogen in the wastewater. Nitrogen in the ammonia form is toxic to certain aquatic organism (USEPA, 2002).

Removal Processes

Ammonium is one of the most commonly encountered nitrogenous pollutants in wastewater (Bodalo et. al., 2005). Loss to the (surface) water gives rise to acidification and eutrophication. Biological removal requires biological nitrification (generally to nitrate). In the case of total nitrogen removal the nitrate must be converted to (di)nitrogen gas. There are several biological processes that can be used if nitrogen removal is required.It can also be removed from wastewater by ion exchange.

Nitrification-Denitrification

The Nitrification-Denitrification process is the most common process for the removal of ammonium from wastewater. Ammonium is first oxidized biologically to nitrate in an aerobic process:

NH₄⁺+ 2O₂ --> NO₃^- + 2H⁺ + H₂O

The process is autotrophic (uses CO2 as carbon source for biomass) and therefore has a low yield and slow growth rate. The produced nitrate is reduced to dinitrogen gas in denitrification. The process takes place anoxically and is coupled to the oxidation of organic material or sulfide:

NO₃^- + COD --> N₂ + CO₂ + biomass

If COD or sulfide is sufficiently available in the wastewater, it will be used in this reaction. In COD-deficient wastewaters however it is added externally (e.g. in the form of methanol, glycerol etc).

Nitritation-Denitritation

Nitrogen removal from wastewater with high nitrogen concentration and low COD/N ratio via nitrite is advantageous (Jenicek et. al., 2004). The combination of nitritation-denitritation is highly beneficial for the domestic wastewater treatment in terms of lower carbon requirements, reduced oxygen demand and less biomass production (Zeng et. al., 2010).

Nitritation-Anammox

It is common to find effluents characterized by low C/N ratios which are usually difficult to be treated by means of conventional nitrification-denitrification processes. For those cases the use of the combined partial nitrification-anammox processes is an option. Both processes can be performed in two units sequentially operated (Van Dongen et al., 2001) in such a way that in the first unit the partial nitrification to nitrite of half of the ammonia contained in the wastewater takes place. This generated media is then fed to a second unit where the anammox process occurs. Another option consists of the use of a single aerobic unit where the biomass grows as a biofilm to perform simultaneously both processes. In the external layers of the biofilm the partial nitrification takes place while the anammox process is carried out in the inner anoxic zones of the biofilm (Sliekers et al. 2002). Both processes are normally operated at temperatures around 30 ºC. When the treated wastewater is characterized by low C/N ratios and low temperatures the use of these combined processes at low temperature is recommended. Recent research indicated that the anammox process can be succesfully operated at temperatures in the range of 20 ºC to treat effluents from anaerobic digesters (Vázquez-Padín et al., 2009).

Disinfectants Chlorine Dioxide

What are the characteristics of chlorine dioxide ?
Chlorine dioxide (ClO₂) is a synthetic, green-yellowish gas with a chlorine-like, irritating odor. Chlorine dioxide is a neutral chlorine compound. Chlorine dioxide is very different from elementary chlorine, both in its chemical structure as in its behavior. Chlorine dioxide is a small, volatile and very strong molecule. In diluted, watery solutions chlorine dioxide is a free radical. At high concentrations it reacts strongly with reducing agents.

How does disinfection by chlorine dioxide work?
Substances of organic nature in bacterial cells react with chlorine dioxide, causing several cellular processes to be interrupted. Chlorine dioxide reacts directly with amino acids and the RNA in the cell. It is not clear whether chlorine dioxide attacks the cell structure or the acids inside the cell. The production of proteins is prevented. Chlorine dioxide affects the cell membrane by changing membrane proteins and fats and by prevention of inhalation.
When bacteria are eliminated, the cell wall is penetrated by chlorine dioxide. Viruses are eliminated in a different way; chlorine dioxide reacts with peptone, a water-soluble substance that originates from hydrolisis of proteins to amino acids. Chlorine dioxide kills viruses by prevention of protein formation.

Why is Chlorine Dioxide so good?

· Potency –

· Rapid kill –

· Not pH sensitive –

· Effective biocide against biofilms –

· Potency against legionella –

· No Halogenated Disinfection By-Products (DBPs) –

· High Selectivity –

· No Taste, Odour and Taint Problems

Applications

Drinking water: Municipal and Commercial buildings
Food & beverages industry
Cooling water
Shower facilities in public swimming pools
Commercial buildings

Environmental laws

In the Constitution of India it is clearly stated that it is the duty of the state to ‘protect and improve the environment and to safeguard the forests and wildlife of the country’. It imposes a duty on every citizen ‘to protect and improve the natural environment including forests, lakes, rivers, and wildlife’. Reference to the environment has also been made in the Directive Principles of State Policy as well as the Fundamental Rights. The Department of Environment was established in India in 1980 to ensure a healthy environment for the country. This later became the Ministry of Environment and Forests in 1985.

The constitutional provisions are backed by a number of laws – acts, rules, and notifications. The EPA (Environment Protection Act), 1986 came into force soon after the Bhopal Gas Tragedy and is considered an umbrella legislation as it fills many gaps in the existing laws. Thereafter a large number of laws came into existence as the problems began arising, for example, Handling and Management of Hazardous Waste Rules in 1989.

Following is a list of the environmental legislations that have come into effect:

General

Forest and wildlife

Water

Air

General

1986 - The Environment (Protection) Act authorizes the central government to protect and improve environmental quality, control and reduce pollution from all sources, and prohibit or restrict the setting and /or operation of any industrial facility on environmental grounds.

1986 - The Environment (Protection) Rules lay down procedures for setting standards of emission or discharge of environmental pollutants.

1989 - The objective of Hazardous Waste (Management and Handling) Rules is to control the generation, collection, treatment, import, storage, and handling of hazardous waste.

1998 - The Biomedical waste (Management and Handling) Rules is a legal binding on the health care institutions to streamline the process of proper handling of hospital waste such as segregation, disposal, collection, and treatment.

1999 - The Environment (Siting for Industrial Projects) Rules, 1999 lay down detailed provisions relating to areas to be avoided for siting of industries, precautionary measures to be taken for site selecting as also the aspects of environmental protection which should have been incorporated during the implementation of the industrial development projects.

2000 - The Municipal Solid Wastes (Management and Handling) Rules, 2000 apply to every municipal authority responsible for the collection, segregation, storage, transportation, processing, and disposal of municipal solid wastes.

2000 - The Ozone Depleting Substances (Regulation and Control) Rules have been laid down for the regulation of production and consumption of ozone depleting substances.

2002 - The Noise Pollution (Regulation and Control) (Amendment) Rules lay down
such terms and conditions as are necessary to reduce noise pollution, permit use of loud speakers or public address systems during night hours (between 10:00 p.m. to 12:00 midnight) on or during any cultural or religious festive occasion

2002 - The Biological Diversity Act is an act to provide for the conservation of biological diversity, sustainable use of its components, and fair and equitable sharing of the benefits arising out of the use of biological resources and knowledge associated with it

Forest and wildlife

1927 - The Indian Forest Act and Amendment, 1984, is one of the many surviving colonial statutes. It was enacted to ‘consolidate the law related to forest, the transit of forest produce, and the duty leviable on timber and other forest produce’.

1972 - The Wildlife Protection Act, Rules 1973 and Amendment 1991 provides for the protection of birds and animals and for all matters that are connected to it whether it be their habitat or the waterhole or the forests that sustain them.

1980 - The Forest (Conservation) Act and Rules, 1981, provides for the protection of and the conservation of the forests.

Water

1897 - The Indian Fisheries Act establishes two sets of penal offences whereby the government can sue any person who uses dynamite or other explosive substance in any way (whether coastal or inland) with intent to catch or destroy any fish or poisonous fish in order to kill.

1956 - The River Boards Act enables the states to enroll the central government in setting up an Advisory River Board to resolve issues in inter-state cooperation.

1970 - The Merchant Shipping Act aims to deal with waste arising from ships along the coastal areas within a specified radius.

1974 - The Water (Prevention and Control of Pollution) Act establishes an institutional structure for preventing and abating water pollution. It establishes standards for water quality and effluent. Polluting industries must seek permission to discharge waste into effluent bodies.
The CPCB (Central Pollution Control Board) was constituted under this act.

1991 - The Coastal Regulation Zone Notification puts regulations on various activities, including construction, are regulated. It gives some protection to the backwaters and estuaries.

Air

1948 – The Factories Act and Amendment in 1987 was the first to express concern for the working environment of the workers. The amendment of 1987 has sharpened its environmental focus and expanded its application to hazardous processes.

1981 - The Air (Prevention and Control of Pollution) Act provides for the control and abatement of air pollution. It entrusts the power of enforcing this act to the CPCB .

1982 - The Air (Prevention and Control of Pollution) Rules defines the procedures of the meetings of the Boards and the powers entrusted to them.

1982 - The Atomic Energy Act deals with the radioactive waste.

1987 - The Air (Prevention and Control of Pollution) Amendment Act empowers the central and state pollution control boards to meet with grave emergencies of air pollution.

1988 - The Motor Vehicles Act states that all hazardous waste is to be properly packaged, labelled, and transported.

Wastewater Treatment Ponds

Wastewater treatment using ponds can be an economical way of treatment which produces effluent that is highly purified. The number and the type of ponds used are the determining factors as to the degree of treatment that is provided.

Another name for wastewater treatment ponds is waste stabilization ponds. We use waste stabilization ponds because these ponds help to stabilize the wastewater before it is passed on to receiving water. They can also be referred to as oxidation ponds or sewage lagoons .

The waste stabilization pond is a biological treatment process , where bacteria use organic matter in the wastewater as food. The three types of bacteria at work in most ponds are the aerobic, anaerobic, and the facultative bacteria.

Facultative lagoons are a type of stabilization pond used for biological treatment of industrial and domestic wastewater. Sewage or organic waste from food or fiber processing may be catabolized in a system of constructed ponds where adequate space is available to provide an average waste retention time exceeding a month. A series of ponds prevents mixing of untreated waste with treated wastewater and allows better control of waste residence time for uniform treatment efficiency.

Facultative ponds are used the most to treat municipal wastewater. The ponds are usually 4 to 6 feet deep and the sludge at the bottom is anaerobic, while the 1 to 2 feet of the top of the pond is aerobic. In the middle, the amount of dissolved oxygen varies and either aerobic or anaerobic decomposition will take place, depending on how much dissolved oxygen is available.

Aerobic Pond

In the aerobic pond oxygen is present throughout the pond and all biological activity is aerobic decomposition. Aerobic ponds are a maximum of two feet deep, so that the sunlight can reach throughout the entire depth of the pond, which will let the algae grow throughout. The oxygen they give off allows aerobic process microorganisms to live. Aerobic ponds are not used in colder climates because they will completely freeze in the winter.

Anaerobic Pond

Anaerobic ponds are normally used to treat high strength concentrated industrial waste and no oxygen is present in the pond. All the biological activity is anaerobic decomposition. These ponds are 8 to 12 feet deep and are anaerobic throughout. Scum forms on the top of the most anaerobic ponds. This scum stops air from mixing with the wastewater. Because there is no dissolved oxygen in the pond the anaerobic bacteria will be a work. The gases that is produced by the anaerobic bacterial action causes odor problems and these types of ponds are not used very often.

Microbial transformations of heavy metals

Environmental biotechnology is the technology of applying mainly microorganisms to improve the quality of the environment. Bioremediation is the use of living organisms to reduce or eliminate environmental hazards resulting from the accumulation of toxic chemicals and other hazardous wastes. This technology is based on the utilisation of naturally occurring or genetically engineered microorganisms to transform organic and inorganic compounds.

Microbial transformation of toxic metals and radionuclides may affect their solubility, mobility, and bioavailability (Francis, 1997). Several of the key microbial processes may affect mobilisation or immobilisation of toxic elements by one or more of the following mechanisms:

–	chelation of elements by metabolites,
–	oxidation-reduction of metals which affect the solubility or valence state,
–	Changes in pH which affect the ionic state,
–	biosorption by functional groups on the cell surface,
–	bioaccumulation by an energy-dependent transport system,
–	immobilisation due to formation of stable materials,
–	biomethylation,
–	biodegradation of organic complex of metals and radionuclides.

Organism	Element
Citrobacter sp.	Lead, Cadmium
Thiobacillus ferrooxidans	Silver
Bacillus cereus	Cadmium
Bacillus subtilis	Chromium
Pseudomonas aeruginosa	Uranium
Micrococcus luteus	Strontium
Rhisopus arrhizus	Mercury
Aspergillus niger	Thorium
Saccharomyces cerevisiae	Uranium

1. MOBILISATION

Dissolution of toxic metals and radionuclides is due to oxidation-reduction reaction and production of mineral or organic acid metabolites, as well as lowering of the pH.

1.1. Enzymatic oxidation

Inorganic compounds that can exist in more than one oxidation state and in which the higher oxidation state is less soluble, enzymatic oxidation may be a useful way for removing the inorganic species from solution.

1.2. Enzymatic reduction

In case of inorganic compounds that can exist in more than one oxidation state and whose reduced state is insoluble, enzymatic reduction may be useful in removing the species from solution.

1.3. Complexation

The use of complexation agents may be useful in mobilizing toxic inorganic compounds to facilitate their removal from solid waste .

1.4. Siderophores

When microorganisms are grown in an iron deficient medium, they produce specific iron chelators, so called siderophores, in the medium. They play an important role in the complexation of toxic metals and radionuclides and increase their solubility.

2. IMMOBILISATION

Immobilisation of toxic metals and radionuclides are brought about by precipitation, biosorption and bioaccumulation. These processes have received considerable attention because of their potential application of waste water treatment containing toxic metals and radionuclides.

2.1. Precipitation

Sulfate reduction is an example for the precipitation of metallic ions in solution. Most metal sulfides are quite insoluble in aqueous solution. The stability of these sulfides depends on the maintenance of anoxic conditions.

2.2. Biosorption

Biosorption of toxic metals and radionuclides is based on non-enzymatic processes such as adsorption (Fig. 2). Adsorption is due to the non-specific binding of ionic species to cell surface-associated or extracellular polysaccharides and proteins.

2.3. Bioaccumulation

Bioaccumulation has been described for such metals as mercury, lead, silver, cadmium, nickel, ¹³⁷cesium, ⁶⁰cobalt, ⁸⁵stroncium, plutonium, and uranium. Intracellular accumulation of toxic elements is carried out by an energy dependent transport system.

Self Purification of Natural Water Systems

Some of the major physical processes in self purification of natural water systems are as follows: (i) Dilution (ii) Sedimentation and Re-suspension (iii) Filtration (iv) Gas Transfer.

The major physical processes involved in self-purification of water courses are dilution, sedimentation and re-suspension, filtration, gas transfer and heat transfer.

These processes are not only important but are also of significance in their relation to certain chemical and biochemical self-purification processes.

(i) Dilution:

In the beginning of twentieth century, waste water disposal practices were based on the premise that “the solution to pollution is dilution”. Dilution was considered as the most economical means of waste water disposal. In this method relatively small quantities of waste are discharged into large bodies of water.’

Although dilution is a powerful adjunct to self-cleaning mechanism of surface waters, its success depends upon discharging relatively small quantities of waste into large bodies of water. Growth in population and industrial activity, with increases in water demand and wastewater quantities, precludes the use of many streams for dilution of raw or poorly treated wastewaters.

(ii) Sedimentation and Re-suspension:

Sources of suspended solids, one of the most common water pollutants, include domestic and industrial wastewater and runoff from agricultural or urban activities. These solids may be inorganic or organic materials and/or live organisms, and they may vary in size from large organic particles to tiny, almost invisible, colloids.

In suspension, solids increase turbidity and the reduced light penetration may restrict the photosynthetic activity of plants, inhibit the vision of aquatic animals, interfere with feeding of aquatic animals that obtain food by filtration, and be abrasive to respiratory structures such as gills offish.

Settling out or sedimentation, is nature’s method of removing suspended particles from a watercourse, and most large solids will settle out readily in quiescent water. Particles in the colloidal size range can stay in suspension for long periods of time, though eventually most of these will also settle out.

Re-suspension of solids is common in times of flooding or heavy runoff. In such cases, increased turbulence may resuspend solids formerly deposited along normally quiescent areas of a stream and carry them for considerable distances downstream. Eventually they will again settle out, but not before their presence has increased the turbidity of the waters into which they have been introduced.

(iii) Filtration:

As large bits of debris wash along a stream bed, they often lodge on reeds or stones where they remain caught until high waters wash them into the mainstream again. Small bits of organic matter or inorganic clays and other sediments may be filtered out by pebbles or rocks along the stream bed.

As water percolates from the surface downward into ground water aquifers, filtration of a much more sophisticated type occurs, and if the soil layers are deep and fine enough, removal of suspended material is essentially complete by the time water enters the aquifer. Many streams interchange freely with the alluvial aquifers underneath them, so the filtered water may re-enter the stream at some point downstream.

(iv) Gas Transfer:

The transfer of gases into and out of water is an important part of the natural purification process. The replenishment of oxygen lost to bacterial degradation of organic waste is accomplished by the transfer of oxygen from the air into the water. Conversely, gases evolved in the water by chemical and biological processes may be transferred from the water to the atmosphere.

Enumerating Microorganisms

Enumerating microbes in a sample is a useful technique. Here we discuss two methods to estimate the number of microbes in a sample. One quick method is to measure turbidity in which the density of cells is measured with a spectrophotometer. A viable count, a second method, requires the dilution of a sample, the dilution is spread on an agar plate with the nutrients for the microbe, and after growth, the scientist counts the colonies formed. Each colony represents growth from one microbe.

The Methods of Enumeration in Microbes

The methods of enumeration in microbes can be divided into four categories. Direct methods involve counting the microbes, while indirect methods involve estimation. Viable methods only count cells that are metabolically active, while total counts include dead and inactive cells.

Direct/Viable

· A direct/viable method involves a standard plate count, in which repeated dilutions of a sample are counted to calculate the count in the original sample.

Indirect/Viable

· Indirect/viable methods such as MPN (most probable number) involve making a statistical inference about the microbe count based on patterns of growth.

Direct/Total

· The microbes are counted with the aid of fluorescent stains and dyes, which make the microbes visible with the aid of a fluorescent microscope.

Indirect/Total

· Spectroscopy is a form of indirect/total enumeration, which involves estimating the amount of microbes based on the amount of light passed through the culture by a spectrophotometer.

Biogas

Biogas typically refers to a mixture of gases produced by the breakdown of organic matter in the absence of oxygen. Biogas can be produced from regionally available raw materials such as recycled waste. It is a renewable energy source and in many cases exerts a very small carbon footprint.

Biogas is produced by anaerobic digestion with anaerobic bacteria or fermentation of biodegradable materials such as manure, sewage, municipal waste, green waste, plant material, and crops.^[1] It is primarily methane (CH
4) and carbon dioxide (CO
2) and may have small amounts of hydrogen sulphide (H
2S), moisture and siloxanes.

The gases methane, hydrogen, and carbon monoxide (CO) can be combusted or oxidized with oxygen. This energy release allows biogas to be used as a fuel; it can be used for any heating purpose, such as cooking. It can also be used in a gas engine to convert the energy in the gas into electricity and heat.

Advantages and Benefits of Biogas

Provides a non-polluting and renewable source of energy.
Efficient way of energy conversion (saves fuelwood).
Saves women and children from drudgery of collection and carrying of firewood, exposure to smoke in the kitchen, and time consumed for cooking and cleaning of utensils.
Produces enriched organic manure, which can supplement or even replace chemical fertilizers.
Leads to improvement in the environment, and sanitation and hygiene.
Provides a source for decentralized power generation.
Leads to employment generation in the rural areas.
Household wastes and bio-wastes can be disposed of usefully and in a healthy manner.
The technology is cheaper and much simpler than those for other bio-fuels, and it is ideal for small scale application.
Dilute waste materials (2-10% solids) can be used as in feed materials.
Any biodegradable matter can be used as substrate.
Anaerobic digestion inactivates pathogens and parasites, and is quite effective in reducing the incidence of water borne diseases.
Environmental benefits on a global scale: Biogas plants significantly lower the greenhouse effects on the earth’s atmosphere. The plants lower methane emissions by entrapping the harmful gas and using it as fuel.

Disadvantages of Biogas

The process is not very attractive economically (as compared to other biofuels) on a large industrial scale.
It is very difficult to enhance the efficiency of biogas systems.
Biogas contains some gases as impurities, which are corrosive to the metal parts of internal combustion engines.
Not feasible to locate at all the locations.

Uses

Biogas is mostly used as a fuel in power generators and boilers. For these uses, the H₂S content in biogas should be less than 200 parts per million (ppm) to ensure a long life for the power and heat generators.

Biogas can also be upgraded to pipeline natural gas quality for use as a renewable natural gas. This upgraded gas may be used for residential heating and as vehicle fuel.

Activated Sludge Process

Activated sludge refers to a mass of microorganisms cultivated in the treatment process to break down organic matter into carbon dioxide, water, and other inorganic compounds. The activated sludge process has three basic components: 1) a reactor in which the microorganisms are kept in suspension, aerated, and in contact with the waste they are treating; 2) liquid-solid separation; and 3) a sludge recycling system for returning activated sludge back to the beginning of the process.

Primary effluent (or plant influent) is mixed with return activated sludge to form mixed liquor. The mixed liquor is aerated for a specified length of time. During the aeration the activated sludge organisms use the available organic matter as food producing stable solids and more organisms. The suspended solids produced by the process and the additional organisms become part of the activated sludge. The solids are then separated from the wastewater in the settling tank. The solids are returned to the influent of the aeration tank (return activated sludge). Periodically the excess solids and organisms are removed from the system (waste activated sludge). Failure to remove waste solids will result in poor performance and loss of solids out of the system over the settling tank effluent weir.

There are a number of factors that affect the performance of an activated sludge treatment system. These include:

temperature
return rates
amount of oxygen available
amount of organic matter available
pH
waste rates
aeration time
wastewater toxicity

To obtain desired level of performance in an activated sludge system, a proper balance must be maintained between the amount of food (organic matter), organisms (activated sludge) and oxygen (dissolved oxygen).

Activated Sludge Modifications

Many activated sludge process modifications exist. Each modification is designed to address specific conditions or problems. Such modifications are characterized by differences in mixing and flow patterns in the aeration basin, and in the manner in which the microorganisms are mixed with the incoming wastewater.

The major process modifications of the activated sludge process are:

conventional
tapered aeration
complete mix
step aeration
contact stabilization
extended aeration
pure oxygen systems

Advantages: Efficient removal of BOD, COD and nutrients when designed and professionally operated according to local requirements. The process itself has flexibility and numerous modifications can be tailored to meet specific requirements (e.g. for nitrogen removal). Activated sludge is the best documented and most widely used form of secondary wastewater treatment.

Disadvantages: Expensive in terms of both capital and O&M costs, requires a constant energy supply, needs trained operators who can monitor the system and react to changes immediately, and the availability of spare parts and chemicals may be an obstacle. The track record of activated sludge plants in the developing world is very poor, and few operate as designed or intended.

Trickling Filter

A Trickling Filter is a fixed bed, biological filter that operates under (mostly) aerobic conditions. Pre-settled wastewater is ‘trickled’ or sprayed over the filter. As the water migrates through the pores of the filter, organics are degraded by the biomass covering the filter material.

The Trickling Filter is filled with a high specific surface-area material such as rocks, gravel, shredded PVC bottles, or special pre-formed filter-material. Pre-treatment is essential to prevent clogging and to ensure efficient treatment. The pre-treated wastewater is ‘trickled’ over the surface of the filter. Organisms that grow in a thin bio-film over the surface of the media oxidize the organic load in the wastewater to carbon dioxide and water while generating new biomass.

The incoming wastewater is sprayed over the filter with the use of a rotating sprinkler. In this way, the filter media goes through cycles of being dosed and exposed to air. However, oxygen is depleted within the biomass and the inner layers may be anoxic or anaerobic.

The filter is usually 1 to 3m deep but filters packed with lighter plastic filling can be up to 12m deep. The ideal filter material has a high surface to volume ratio, is light, durable and allows air to circulate. Whenever it is available, crushed rock or gravel is the cheapest option. The particles should be uniform such that 95% of the particles have a diameter between 7 and 10cm. Both ends of the filter are ventilated to allow oxygen to travel the length of the filter. A perforated slab that allows the effluent and excess sludge to be collected supports the bottom of the filter.

With time, the biomass will grow thick and the attached layer will be deprived of oxygen; it will enter an endogenous state, will lose its ability to stay attached and will slough off. High-rate loading conditions will also cause sloughing. The collected effluent should be clarified in a settling tank to remove any biomass that may have dislodged from the filter. The hydraulic and nutrient loading rate (i.e. how much wastewater can be applied to the filter) is determined based on the characteristics of the wastewater, the type of filter media, the ambient temperature, and the discharge requirements.

Types

the treatment of small individual residential or rural sewage
large centralized systems for treatment of municipal sewage
systems applied to the treatment of industrial wastewater.

Advantages	Disadvantages/limitations
- Can be operated at a range of organic and hydraulic loading rates. - Small land area required compared to Constructed Wetlands.	- High capital costs and moderate operating costs - Requires expert design and construction. - Requires constant source of electricity and constant wastewater flow. - Flies and odours are often problematic. - Not all parts and materials may be available locally. - Pre-treatment is required to prevent clogging. - Dosing system requires more complex engineering.

Sequencing Batch Reactor

The Sequencing Batch Reactor (SBR) is an activated sludge process designed to operate under non-steady state conditions. An SBR operates in a true batch mode with aeration and sludge settlement both occurring in the same tank. The major differences between SBR and conventional continuous-flow, activated sludge system is that the SBR tank carries out the functions of equalization aeration and sedimentation in a time sequence rather than in the conventional space sequence of continuous-flow systems.

Sequencing Batch Reactor Process Cycles

The operating principles of a batch activated sludge process, or SBR, are characterized in six discrete periods:

1. Anoxic Fill
2. Aerated Fill
3. React
4. Settle
5. Decant
6. Idle

Anoxic Fill

The influent wastewater is distributed throughout the settled sludge through the influent distribution manifold to provide good contact between the microorganisms and the substrate [1]. The influent can be either pumped in allowed to flow in by gravity. Most of this period occurs without aeration to create an environment that favors the procreation of microorganisms with good settling characteristics. Aeration begins at the beginning of this period.

Aerated Fill

Mixed liquor is drawn through the manifold, mixed with the influent flow in the motive liquid pump, and discharged, as motive liquid, to the jet aerator [1]. This initiates the feast period. Feast is when the microorganisms have been in contact with the substrate and a large amount of oxygen is provided to facilitate the substrate consumption. Nitrification and denitrification occurs at the beginning of this stage. This period ends when the tank is either full or when a maximum time for filling is reached.

React

During this period aeration continues until complete biodegradation of BOD and nitrogen is achieved. After the substrate is consumed famine stage starts. During this stage some microorganisms will die because of the lack of food and will help reduce the volume of the settling sludge. The length of the aeration period determines the degree of BOD consumption.

Settle

Aeration is discontinued at this stage and solids separation takes place leaving clear, treated effluent above the sludge blanket. During this clarifying period no liquids should enter or leave the tank to avoid turbulence in the supernatant.

Decant

This period is characterized by the withdrawal of treated effluent from approximately two feet below the surface of the mixed liquor by the floating solids excluding decanter [1]. This removal must be done without disturbing the settled sludge.

Idle

The time in this stage can be used to waste sludge or perform backwashing of the jet aerator. The wasted sludge is pumped to an anaerobic digester to reduce the volume of the sludge to be discarded. The frequency of sludge wasting ranges between once each cycle to once every two to three months depending upon system design.

Rotating Biological Contactors

The rotating biological contactor (RBC) is a fixed film biological secondary treatment device. The basic process is similar to that occurring in the trickling filter. In operation, a media, consisting of a series of circular disks mounted side by side on a common shaft is rotated through the wastewater flow.

The surface of the disk is covered with a biological slime similar to that on the media of a trickling filter. RBC units are usually installed in a concrete tank so that the surface of the wastewater passing through the tank almost reaches the shaft. This means that about 40% of the total surface area of the disks is always submerged. The shaft continually rotates at 1 to 2 rpm, and a layer of biological growth 2 to 4 mm thick is soon established on the wetted surface of each disk. The organisms in the slime assimilate (remove) organic matter from the wastewater for aerobic decomposition. The disk continues to rotate, leaving the wastewater and moving through the air. During this time, oxygen is transferred from the air to the slime. As the slime reenters the wastewater, excess solids and waste products are stripped off the media as sloughings. These sloughings are transported with the wastewater flow t a settling tank for removal.

Typically, a single contactor is not sufficient to achieve the desired level of treatment, so a group of contactors are used in series. Each individual contactor is called a stage and the group is known as a train. Most RBC systems consist of two or more trains with three or more stages in each. One major advantage of the RBC system is the level of nitrification that can be achieved if sufficient stages are provided.

During operation, observations of the RBC movement, slime color, and appearance are helpful in determining system performance; that is, they can indicate process conditions. If the unit is covered, observations are usually limited to that portion of the media that can be viewed through the access door. The following may be observed:

Gray, shaggy slime growth - indicates normal operation
Reddish brown, golden shaggy growth - nitrification
White chalky appearance - high sulfur concentrations
No slime - severe temperature or pH changes

In regard to typical performance, a well-maintained, properly operated RBC typically produces a high quality effluent with BOD at 8-95% and Suspended Solids Removal at 85-95%. The process may also reduce the levels of organic nitrogen and ammonia nitrogen significantly if designed for this purpose.

Advantages

Short contact periods are required because of the large active surface.
RBCs are capable of handling a wide range of flows.
Sloughed biomass generally has good settling characteristics and can easily be separated from the waste stream.
Operating costs are low because little skill is required in plant operation.
Short retention time.
Low power requirements.
Elimination of the channeling to which conventional percolators are susceptible.
Low sludge production and excellent process control.

Disadvantages

Disadvantages of RBCs include:

Requirement for covering RBC units in northern climates to protect against freezing.
Shaft bearings and mechanical drive units require frequent maintenance.

Anaerobic Filter

An Anaerobic Filter is a fixed-bed biological reactor. As wastewater flows through the filter, particles are trapped and organic matter is degraded by the biomass that is attached to the filter material.
This technology consists of a sedimentation tank (or Septic Tank) followed by one or more filter chambers. Filter material commonly used includes gravel, crushed rocks, cinder, or specially formed plastic pieces. Typical filter material sizes range from 12 to 55mm in diameter. Ideally, the material will provide between 90 to 300m2 of surface area per 1m3 of reactor volume. By providing a large surface area for the bacterial mass, there is increased contact between the organic matter and the active biomass that effectively degrades it.

The Anaerobic Filter can be operated in either upflow or downflow mode. The upflow mode is recommended because there is less risk that the fixed biomass will be washed out. The water level should cover the filter media by at least 0.3m to guarantee an even flow regime.

Studies have shown that the HRT is the most important design parameter influencing filter performance. An HRT of 0.5 to 1.5 days is a typical and recommended. A maximum surface-loading (i.e. flow per area) rate of 2.8m/d has proven to be suitable. Suspended solids and BOD removal can be as high as 85% to 90% but is typically between 50% and 80%. Nitrogen removal is limited and normally does not exceed 15% in terms of total nitrogen (TN).

Advantages	Disadvantages/limitations
- Resistant to organic and hydraulic shock loads. - No electrical energy required. - Can be built and repaired with locally available materials. - Long service life. - Moderate capital costs, moderate operating costs depending on emptying; can be lowered depending on number of users. - High reduction of BOD and solids.	- Requires constant source of water. - Effluent require secondary treatment and/or appropriate discharge. - Low reduction of pathogens and nutrients. - Requires expert design and construction. - Long start up time.

Expanded-Bed Adsorption

Expanded bed adsorption (EBA) is a preparative chromatographic technique which makes processing of viscous and particulate liquids possible.

EBA uses apparatus that is familiar to most users of standard liquid chromatography. The column has a flow adapter that is positioned to suit the specific step of resin preparation or protein purification. And a series of pumps and valves, connected through the adapter and bottom of the column, control the flow rate and direction of the buffer and sample loading

In more traditional packed-bed methods, in which the resin is confined between the bottom of the column and the flow adapter, clogging occurs when particulate matter and cell debris are unable to flow around the closely packed resin beads. By contrast, EBA columns are fed from below, and the adapter is held away from the packed-resin level, giving the resin room to expand and thus creating spaces between the beads. Figure 1 illustrates this phenomenon schematically. When the resin is packed in the column, the beads sit close together and leave little room for large aggregates and clumps to maneuver (Figure 1-1).

As buffer is injected from below, the resin becomes fluidized, and the beads form a stable concentration gradient when their sedimentation velocity equals the upward liquid flow velocity (Figure 1-2).

Unlike traditional resins, in which the beads tend to be relatively uniform in size, the beads of EBA resins are variable, typically ranging from 50 to 400 mm. Thus, the larger particles populate the lower portion of the fluidized bed while the smaller particles populate the upper portion. If the beads are too small, expansion will occur at velocities comparable to the escape velocity of the particulate contaminants, lowering purification efficiency. Likewise, if the resin beads are too large, fluidization requires higher flow rates, and protein binding is impaired because of improper diffusion among the beads.

As the sample feedlot is injected, the particulates and cell debris move freely around the resin beads and eventually leave through the top of the column. As with any chromatographic step, the resin then undergoes strenuous washing to limit nonspecific interactions between the particulates and resin. Meanwhile, the compounds of interest interact with the beads and are retained on the column (Figure 1-3). The column is then allowed to repack, the flow is reversed, and the compound is eluted from the beads as with traditional methods (Figure 1-4).

It is this last step that separates EBA from both batch-mode and fluidized-bed adsorption chromatography. In the latter methods, the compounds of interest can only be eluted from the resin in a batch- or stepwise manner, and so there is little or no resolution of eluted molecules. By contrast, a repacked column allows the use of elution gradients and improves elution peak resolution.

Applications

With the ability to practically ignore particulate contamination, EBA allows researchers to purify products from a wide variety of sources and conditions. Since its development in the early 1990s, the range of samples has expanded to include secreted, extracted, and solubilized proteins from bacteria, yeast (Saccharomyces cerevisiae and Pichia pastoris), plant tissues, mammalian tissue culture, and milk.

Upflow Anaerobic Sludge Blanket Reactor

The Upflow Anaerobic Sludge Blanket Reactor (UASB) is a single tank process. Wastewater enters the reactor from the bottom, and flows upward. A suspended sludge blanket filters and treats the wastewater as the wastewater flows through it.

The sludge blanket is comprised of microbial granules, i.e. small agglomerations (0.5 to 2mm in diameter) of microorganisms that, because of their weight, resist being washed out in the upflow. The microorganisms in the sludge layer degrade organic compounds. As a result, gases (methane and carbon dioxide) are released. The rising bubbles mix the sludge without the assistance of any mechanical parts. Sloped walls deflect material that reaches the top of the tank downwards. The clarified effluent is extracted from the top of the tank in an area above the sloped walls.

After several weeks of use, larger granules of sludge form which in turn act as filters for smaller particles as the effluent rises through the cushion of sludge. Because of the upflow regime, granule-forming organisms are preferentially accumulated as the others are washed out.

The gas that rises to the top is collected in a gas collection dome and can be used as energy (biogas). An upflow velocity of 0.6 to 0.9m/h must be maintained to keep the sludge blanket in suspension.

Advantages	Disadvantages/limitations
- High reduction in organics. - Can withstand high organic loading rates (up to 10kg BOD/m3/d) and high hydraulic loading rates. - Low production sludge (and thus, infrequent desludging required). - Biogas can be used for energy (but usually requires scrubbing first).	- Difficult to maintain proper hydraulic conditions (upflow and settling rate must be balanced). - Long start up time. - Treatment may be unstable with variable hydraulic and organic loads. - Constant source of electricity is required. - Not all parts and materials may be available locally. - Requires expert design and construction supervision.

Packed bed reactor

Kinds of Phases Present	Usage	Advantages	Disadvantages
1. Gas phase/ solid catalyzed 2. Gas-solid mix	1. Used primarily in heterogeneous has phase reactions with a catalyst	1. High conversion per unit mass of catalyst 2. Low operating cost 3. Continuous operation	1. Undesired thermal gradients may exist 2. Poor temperature control 3. Channeling may occur 4. Unit may be difficult to service and clean

In chemical processing, a packed bed is a hollow tube, pipe, or other vessel that is filled with a packing material. The packing can be randomly filled with small objects like Raschig rings or else it can be a specifically designed structured packing. Packed beds may also contain catalyst particles or adsorbents such as zeolite pellets, granular activated carbon, etc.

The purpose of a packed bed is typically to improve contact between two phases in a chemical or similar process. Packed beds can be used in a chemical reactor, a distillation process, or a scrubber, but packed beds have also been used to store heat in chemical plants. In this case, hot gases are allowed to escape through a vessel that is packed with a refractory material until the packing is hot. Air or other cool gas is then fed back to the plant through the hot bed, thereby pre-heating the air or gas feed.

Anaerobic Contact Process

Anaerobic contact reactors employ an external clarifier or vessel to settle solids and subsequently recycle them back to the reactor tank. Typical configurations include large tanks due to the low organic and hydraulic loading rates employed in their design. Anaerobic contact systems are particularly effective when granulation is difficult or wastewater contains higher than desirable amounts of troublesome constituents, e.g. O&G, suspended solids. Anaerobic contact alternatives are effective at successfully retaining flocculent, i.e. nongranular sludge, thus permiting maintaining appropriate anaerobic biomass inventory levels.

Hybrid Anaerobic Reactors

The hybrid reactor design combines an lower section functionally identical to an UASB and an upflow AF on top, the idea being to combine the strengths of each approach in a single tank. Thus, the lowermost 30 to 50 percent UASB-like portion of the reactor volume is responsible for flocculant and/or granular sludge formation. The upper 50 to 70 percent of the reactor is filled with crossflow plastic media and behaves as an anaerobic filter.

Advantages of the hybrid anaerobic reactor design include:

granular sludge formation is not essential, i.e. flocculant sludge will perform satisfactorily and attain good stability at relatively high loadings
biomass developed in the fixed media section add to the reactor's inventory

The hybrid reactor has been particularly suitable for treating wastewaters where granular sludge development is difficult such as some chemical industries wastes. The attached growth on the media in the upper portion of the reactor together with the formation of a granular or flocculent sludge bed in the bottom section help add up significant biomass inventories leading to increased process stability and higher removal. The crossflow media modules also act as effective gas-liquid-solids separator further enhancing biomass retention.

Biosensor

A biosensor is an analytical device, used for the detection of an analyte, that combines a biological component with a physicochemical detector.^[1][2]

the sensitive biological element (e.g. tissue, microorganisms, organelles, cell receptors, enzymes, antibodies, nucleic acids, etc.), a biologically derived material or biomimetic component that interacts (binds or recognizes) the analyte under study. The biologically sensitive elements can also be created by biological engineering.
the transducer or the detector element (works in a physicochemical way; optical, piezoelectric, electrochemical, etc.) that transforms the signal resulting from the interaction of the analyte with the biological element into another signal (i.e., transduces) that can be more easily measured and quantified;
biosensor reader device with the associated electronics or signal processors that are primarily responsible for the display of the results in a user-friendly way.^[3] This sometimes accounts for the most expensive part of the sensor device, however it is possible to generate a user friendly display that includes transducer and sensitive element(see Holographic Sensor). The readers are usually custom-designed and manufactured to suit the different working principles of biosensors.

Parts of a biosensor

Every biosensor comprises:

A biological component that acts as the sensor
An electronic component that detects and transmits the signal

Biosensor elements

A variety of substances may be used as the bioelement in a biosensor. Examples of these include:

Nucleic acids
Proteins including enzymes and antibodies. Antibody-based biosensors are also called immunosensors.
Plant proteins or lectins
Complex materials like tissue slices, microorganisms and organelles

The signal generated when the sensor interacts with the analyte may be electrical, optical or thermal. It is then converted by means of a suitable transducer into a measurable electrical parameter – usually a current or voltage.

Applications

There are many potential applications of biosensors of various types. The main requirements for a biosensor approach to be valuable in terms of research and commercial applications are the identification of a target molecule, availability of a suitable biological recognition element, and the potential for disposable portable detection systems to be preferred to sensitive laboratory-based techniques in some situations. Some examples are given below:

Glucose monitoring in diabetes patients ←historical market driver
Other medical health related targets
Environmental applications e.g. the detection of pesticides and river water contaminants such as heavy metal ions^[36]
Remote sensing of airborne bacteria e.g. in counter-bioterrorist activities
Detection of pathogens^[37]
Determining levels of toxic substances before and after bioremediation
Detection and determining of organophosphate
Routine analytical measurement of folic acid, biotin, vitamin B12 and pantothenic acid as an alternative to microbiological assay
Determination of drug residues in food, such as antibiotics and growth promoters, particularly meat and honey.
Drug discovery and evaluation of biological activity of new compounds.
Protein engineering in biosensors^[38]
Detection of toxic metabolites such as mycotoxins

Fluidized bed reactor

A fluidized bed reactor (FBR) is a type of reactor device that can be used to carry out a variety of multiphase chemical reactions. In this type of reactor, a fluid (gas or liquid) is passed through a granular solid material (usually a catalyst possibly shaped as tiny spheres) at high enough velocities to suspend the solid and cause it to behave as though it were a fluid. This process, known as fluidization, imparts many important advantages to the FBR. As a result, the fluidized bed reactor is now used in many industrial applications.

Basic principles

The solid substrate (the catalytic material upon which chemical species react) material in the fluidized bed reactor is typically supported by a porous plate, known as a distributor.^[1] The fluid is then forced through the distributor up through the solid material. At lower fluid velocities, the solids remain in place as the fluid passes through the voids in the material. This is known as a packed bed reactor. As the fluid velocity is increased, the reactor will reach a stage where the force of the fluid on the solids is enough to balance the weight of the solid material. This stage is known as incipient fluidization and occurs at this minimum fluidization velocity. Once this minimum velocity is surpassed, the contents of the reactor bed begin to expand and swirl around much like an agitated tank or boiling pot of water. The reactor is now a fluidized bed. Depending on the operating conditions and properties of solid phase various flow regimes can be observed in this reactor.

Advantages

The increase in fluidized bed reactor use in today's industrial world is largely due to the inherent advantages of the technology.^[8]

Uniform Particle Mixing: Due to the intrinsic fluid-like behavior of the solid material, fluidized beds do not experience poor mixing as in packed beds. This complete mixing allows for a uniform product that can often be hard to achieve in other reactor designs.
Uniform Temperature Gradients: Many chemical reactions require the addition or removal of heat. Local hot or cold spots within the reaction bed, often a problem in packed beds, are avoided in a fluidized situation such as an FBR.
Ability to Operate Reactor in Continuous State: The fluidized bed nature of these reactors allows for the ability to continuously withdraw product and introduce new reactants into the reaction vessel. Operating at a continuous process state allows manufacturers to produce their various products more efficiently due to the removal of startup conditions in batch processes.

Disadvantage

As in any design, the fluidized bed reactor does have it draw-backs, which any reactor designer must take into consideration.^[8]

Increased Reactor Vessel Size:
Pumping Requirements and Pressure Drop:
Particle Entrainment:
Lack of Current Understanding:
Erosion of Internal Components:
Pressure Loss Scenarios:

Venturi scrubber

A venturi scrubber is designed to effectively use the energy from the inlet gas stream to atomize the liquid being used to scrub the gas stream. This type of technology is a part of the group of air pollution controls collectively referred to as wet scrubbers.

A venturi scrubber consists of three sections: a converging section, a throat section, and a diverging section. The inlet gas stream enters the converging section and, as the area decreases, gas velocity increases (in accordance with the Bernoulli equation). Liquid is introduced either at the throat or at the entrance to the converging section.

The inlet gas, forced to move at extremely high velocities in the small throat section, shears the liquid from its walls, producing an enormous number of very tiny droplets.

Particle and gas removal occur in the throat section as the inlet gas stream mixes with the fog of tiny liquid droplets. The inlet stream then exits through the diverging section, where it is forced to slow down.

Venturis can be used to collect both particulate and gaseous pollutants, but they are more effective in removing particles than gaseous pollutants.

Liquid can be injected at the converging section or at the throat. Thus, the liquid coats the venturi throat making it very effective for handling hot, dry inlet gas that contains dust. Otherwise, the dust would have a tendency to cake on or abrade a dry throat. These venturis are sometimes referred to as having a wetted approach.

Since it is sprayed at or just before the throat, it does not actually coat the throat surface. These throats are susceptible to solids buildup when the throat is dry. They are also susceptible to abrasion by dust particles. These venturis are best used when the inlet stream is cool and moist. These venturis are referred to as having a non-wetted approach.

Venturi scrubbers have following typical industrial applications:
a. Boiler waste gases utilizing coal, oil, biomass and liquid waste
b. Metal Processing – Iron & Steel, Aluminum
c. Wood, Pulp & Paper Industry
d. Chemical Industries
e. Municipal Solid Waste Incinerators

Pollution monitoring and measurement

SO₂ concentration is measured by the ultraviolet fluorescence method, where the analysed sample is exposed to UV-lamp irradiation with energetic excitation of SO₂ molecule. With the backward conversion of the molecule into the basic energetic level, energy as fluorescing radiation is released. This radiation is proportional to the sulfur dioxide concentration and is detected by a photomultiplier.

NO_x concentration is measured by a chemiluminescence analyzer for the NO, NO₂ and NO_x concentration measurement. The principle of this method stands on the nitrogen molecule excitation by ozone. With the conversion of the molecule into the basic energetic level, liberation of radiation as chemiluminescence occurs. This radiation is detected by a photomultiplier. The analyzer design makes possible the acquirement of information on nitrogen monoxide (NO), nitrogen dioxide (NO₂) and nitrogen oxides (NO_x) concentrations.

For PM₁₀ concentration (suspended particulate matter fraction up to 10µm particle size) measurement the radiometric method is used. It stands on beta-ray absorption in a sample captured on filtering material. The difference between the beta-ray absorption of the exposed and non-exposed filtering material, which is proportional to the mass of the captured suspended particle matter, gives the information on its concentration.

The automated stations installed by the State Health Institute and some stations of the Public Health Service use for the suspended particulate matter continual monitoring the tapered element oscillating microbalance(TEOM). It measures the mass of the sample captured on a replaceable filter according to the oscillating tapered element frequency variation. The air sample passes through a filter where the dust particles are captured and runs through a hollow tapered element to a vacuum pump with an electronic flow control.

CO concentration is measured by the method of IR-correlation absorption spectrometry. The radiation from an infra-red source passes through two parallel cells, one of which contains a non-absorbing background gas, the other contains the analyzed flowing sample of ambient air. The difference in energy between the sample and the reference cell is proportional to the carbon monoxide concentration.

The ozone concentration measurement is based on ultraviolet absorption photometry, resting upon absorption of radiation with the wavelenght of 254 nm by ozone in the analyzed sample. The radiation source is an UV-lamp and clean air (zero) and the sample itself are alternately measured in cells. The presented method with automatic pressure and temperature compensation meets the challenging requirements for O₃ measurement.

During the year 1997 continual measurement of aromatic hydrocarbons (benzene, toluene and xylenes) by BTX analyzers and gas chromatography method was introduced at two AMS (Libuš, Most). It is a case of standard linkage to a sampling probe in a container.

METHODS & EQUIPMENTS TO CONTROL AIR POLLUTION

Stationary sources of air pollution emissions, such as power plants, steel mills, smelters, cement plants, refineries, and other industrial processes, release contaminants into the atmosphere as particulates, aerosols, vapors, or gases. These emissions are typically controlled to high efficiencies using a wide range of air pollution control devices. The selection of the appropriate control technology is determined by the pollutant collected, the stationary source conditions, and the control efficiency required. In some cases, pollutant emissions can be reduced significantly through process modifications and combustion controls. However, in most instances, some form of add-on pollution control equipment is installed in the ductwork (or flues) leading to the smoke stack to meet current allowable emission limits.

Methods of controlling gaseous pollutants:

• destroying pollutants by thermal or catalytic combustion, such as by use of a flare stack, a high temperature incinerator, or a catalytic combustion reactor;

• changing pollutants to less harmful forms through chemical reactions, such as converting nitrogen oxides (NOx) to nitrogen and water through the addition of ammonia to the flue gas in front of a selective catalytic reactor; and

• Collecting pollutants using air pollution control systems before they reach the atmosphere.

The air pollution caused by gaseous pollutants like hydrocarbons,sulphur dioxide,ammonia,carbon monoxide,etc can be controlled by using three different methods-Combustion,Absorption and Adsorption.

Combustion:This technique is applied when the pollutants are organic gases or vapours.The organic air pollutants are subjected to 'flame combustion or catalytic combustion' when they are converted to less harmful product carbon dioxide and a harmless product water.
Absorption:In this method,the polluted air containing gaseous pollutants is passed through a scrubber containing a suitable liquid absorbent.The liquid absorbs the harmful gaseous pollutants present in air.
Adsorption:In this method,the polluted air is passed through porous solid adsorbents kept in suitable containers.The gaseous pollutants are adsorbed at the surface of the porous solid and clean air passes through.

Equipments of controlling gaseous pollutants:

INCINERATORS

Incineration involves the high efficiency combustion of certain solid, liquid, or gaseous wastes. The reactions may be self-sustaining based on the combustibility of the waste, or may require the addition of auxiliary fuels, such as natural gas or propane. They may be batch operations or continuous as with flares used to burn off methane from landfills. When not burning solids, they are also called thermal oxidizers, and these devices can operate at efficiencies of 99.99% (as with hazardous waste incinerators).

ABSORPTION & WET SCRUBBING EQUIPMENT

Scrubbing is a physical process whereby particulates, vapors, and gases are controlled by either passing a gas stream through a liquid solution or spraying a liquid into a gas stream.

Water is the most commonly used absorbent liquid. As the gas stream contacts the liquid, the liquid absorbs the pollutants. Gas absorption is commonly used to recover products or to purify gas streams that have high concentrations of water-soluble compounds. Absorption equipment is designed to get as much mixing between the gas and liquid as possible.

Common types of gas absorption equipment include spray towers, packed towers, tray

towers, and spray chambers. Packed towers are by far the most commonly used control

equipment for the absorption of gaseous pollutants.

Scrubbers use a liquid stream to remove solid particles from a gas stream by impacting

these particles with water droplets either through water spraying into the gas or through

violent mixing of water with the gas stream.

Water is directed into the gas stream either immediately before or at the venture throat.

The difference in velocity and pressure resulting from the constriction causes many small and larger water droplets to form. These droplets then collide with the particulates and essentially stick to them. The reduced velocity at the expanded end of the venture throat allows droplets of water containing the particles to coalesce into larger droplets, which then drop out of the gas stream. Often a large cyclonic section is placed after the venture to improve fallout of PM-laden water.

Wet scrubbers can be highly effective in removing particles, with removal efficiencies of up to 99%; however, their efficiency for very small particles can be much lower. Wet scrubbers produce a wastewater stream that will likely require treatment before reuse or discharge.

When possible, collected PM is separated from the water, and the water is reused, but this is often difficult; disposal of a wet sludge by-product is often required.

ADSORPTION

The process of adsorption involves the molecular attraction of gases or vapors (usually volatile organic compounds (VOCs)) onto the surface of certain solids (usually carbon, molecular sieves, and/or catalysts). This attraction may be chemical or physical in nature and is predominantly a surface effect. Activated carbon charcoal), which possesses the large internal surface area needed to adsorb large quantities of gases within its structure, is often used to remove VOCs from flue gases. After the activated carbon is saturated with VOCs, it is often treated (by heat and/or steam) to strip off the collected VOCs. The VOCs are then sent for further treatment, and the carbon is reused in the adsorption reactor. Adsorption is affected by the temperature, flowrate, concentration, and molecular structure of the gas.

Adsorption is commonly used for removing gases from contaminated soil, oil refineries, municipal wastewater treatment plants, industrial paint shops, and steel mills.

FABRIC FILTERS OR BAG HOUSES

Fabric filters, also commonly referred to as bag houses, are used in many industrial applications. They operate in a manner similar to a household vacuum cleaner. Dust-laden gases pass through fabric bags where the dry particulates are captured on the fabric surface. After enough dust has built up on the filters, as indicated by a build up in pressure across the fabric, dust is periodically removed by blowing air back through the fabric, pulsing the fabric with a blast of air, or shaking the fabric. Dust from the fabric then falls to a collection hopper where it is removed. As dust builds up on the fabric, the dust layer itself can act as a filter aid improving the removal efficiency of the device.

CATALYTIC REACTORS

Catalytic reactors, referred to as selective catalytic reduction (SCR) systems, are used extensively to control NOx emissions arising from the burning of fossil fuels in industrial processes. Ammonia is injected and mixed with the flue gases upstream of the SCR reactor. In the SCR reactor, ammonia and NOx react to form nitrogen and water. Greater than 90% NOx removal is possible with these systems.

CYCLONES

Dust-laden gas is whirled rapidly inside a collector shaped like a cylinder (or cyclone). The swirling motion creates centrifugal forces that cause the particles to be thrown against the walls of the cylinder and drop into a hopper below. The gas left in the middle of the cylinder after the dust particles have been removed moves upward and exits the cylinder. Cyclones operate to collect relatively large size PM from a gaseous stream, and can operate at elevated temperatures. Cyclones are typically used for the removal of particles 50 microns (μm) or larger. Efficiencies greater than 90% for particle sizes of 10 μm or greater are possible, and efficiency increases exponentially with particle diameter and with increased pressure drop through the cyclone.

ELECTROSTATIC PRECIPITATORS (ESPS)

ESPs are relatively large, low velocity dust collection devices that remove particles in much the same way that static electricity in clothing picks up small pieces of lint. Transformers are used to develop extremely high voltage drops between charging electrodes and collecting plates. The electrical field produced in the gas stream as it passes through the high voltage discharge introduces a charge on the particles, which is then attracted to the collecting plates. Periodically the collected dust is removed from the collecting plates by a hammer device striking the top of the plates (rapping) dislodging the particulate, which falls to a bottom hopper for removal.

Dry deposition

In aerosol physics, deposition is the process by which aerosol particles collect or deposit themselves on solid surfaces, decreasing the concentration of the particles in the air. It can be divided into two sub-processes: dry and wet deposition. Dry deposition is a continuous process, while wet removal can be realized only in the presence of precipitation. Therefore, despite of the dry process is slower than wet deposition, the accumulated removal quantity of a pollutant could be more important in case of dry deposition. Both the dry and wet depositions depend on the properties of the gases or particles like : near-surface concentration, physical and chemical properties of tracer, weather condition, soil, surface, vegetation properties, chemical reactions.

Dry deposition is caused by:

Gravitational sedimentation – the settling of particles fall down due to gravity.
Interception. This is when small particles follow the streamlines, but if they flow too close to an obstacle, they may collide (e.g. a branch of a tree).
Impaction. This is when small particles interfacing a bigger obstacle are not able to follow the curved streamlines of the flow due to their inertia, so they hit or impact the droplet. The larger the masses of the small particles facing the big one, the greater the displacement from the flow streamline.
Diffusion or Brownian motion. This is the process by which aerosol particles move randomly due to collisions with gas molecules. Such collisions may lead to further collisions with either obstacles or surfaces. There is a net flux towards lower concentrations.
Turbulence. Turbulent eddies in the air transfer particles which can collide. Again, there is a net flux towards lower concentrations.
Other processes, such as: thermophoresis, turbophoresis, diffusiophoresis and electrophoresis.

Color coding

Segregating clinical waste at the point of generation is critical to the safe management of healthcare wastes, which not only aids in the management costs of these wastes, but ensures that the waste is stored, transported and ultimately disposed of correctly.

For clinical waste segregation to work effectively the HTM 07-01 (The Safe Management of Healthcare Waste Memorandum), which is the best practice guidelines published by The Environment Agency for the healthcare sector, recommends that colour coded bins, sacks and waste receptacles are provided to enable easy identification and are placed as close to the point of waste creation as possible.

Waste Type	Classification	Colour Coding	Description
Infectious Clinical Waste	Hazardous	Yellow	Poses a known or potential risk of infection including anatomical waste, diagnostic specimens, regent or test vials.
Infectious Clinical Waste	Hazardous	Orange	Potentially infectious waste, autoclave and laboratory waste.
Offensive/non infectious waste	Non Hazardous	Yellow and Black	Healthcare waste which is classed as non infectious, including nappy, incontinence, sanitary waste and other waste produced from human hygiene.
Pharmaceutical waste	Non Hazardous	Blue	Includes expired, unused, contaminated and spilt pharmaceutical drugs, products and vaccines. Including bottles, boxes or vials with residues. Also including products contaminated from the use of handling pharmaceuticals including gloves, masks, connecting tubes, syringe bodies and drug vials.*
Cytotoxic and Cytostatic drugs	Hazardous	Purple	Hormone and cancer treatment medicinal waste must be separated from other medicinal waste as they are classed as hazardous. Located list can be found in BNF or NIOSH list of medicines. Failure to segregate from non-hazardous medicines will mean that the waste must be treated as hazardous and incur associated hazardous waste charges.
Domestic	Non Hazardous	Black	Domestics waste
Medicinal waste	Non Hazardous	Green	Non Hazardous medicinal waste by incineration
Controlled drugs	Non Hazardous	Blue	Controlled drugs must be denatured to render them safe and without value and then disposed of with other non hazardous waste medicines.*

Clinical waste management
segregation and colour coding guidance

AUTOTHERMAL THERMOPHILIC AEROBIC DIGESTION

The autothermal thermophilic aerobic digestion (ATAD) is one of the well-recognized technologies for the treatment of sludge produced by municipal wastewater treatment plants. In this type of bioreactor, the temperature rises over 50 ^OC due to the conservation of a part of the heat produced by the aerobic metabolism of the microorganisms that consume the abundant organic material present in the sludge. The main benefit of ATAD is its efficiency to kill pathogenic organisms. However, compared to other processes, the number of full scale installations is low.

Since its first steps of development, aerobic thermophilic digestion has been proposed as a process that could be used for the treatment of livestock wastes that are in liquid form. This applies mainly to pig manure but also, in certain cases, to cattle manure. In addition to the pathogen-killing effect, claimed benefits were the simplicity of the process, its robustness, a higher reaction rate (and consequently smaller bioreactors), the conservation of nitrogen and the possibility of heat recovery. Nevertheless, full-scale aerobic thermophilic plants for liquid manure are scarce and most of them have been set for experimental purposes.

ATAD is an energy intensive process because of the high oxygen uptake rates of thermophilic microorganisms.

Physical, chemical and biological transformations occurring during the operation of the ATAD reactor are described by means of dynamic models, which are suitable tools to optimize process operation. Input process parameters are usually uncertain, and they must be estimated or assumed to be known in advance. Some of them can only be completely specified immediately before process implementation.

Monday, September 7, 2015

ENVIRONMENT BIOTECHNOLOGY PART 1

Carbon Monoxide (CO)

Sulfur Dioxide (SO2)

Nitrogen Oxides (NOx)

Ozone (O3)

Lead (Pb)

Particulate Matter

Control of Soil Pollution

Water Pollutants

Parameters to Monitor Septic System Performance

Bioremediation

2. How does it work?

Advantages

Application

Advantages and limitations

Common PhACs found in the environment

Analgesics (anti-inflammatory and antipyretic)

Antibiotics

Test Limitations[edit]

Toxicity[edit]

Appropriate Microbial Population[edit]

Sulphur Cycle

Steps of Sulfur Cycle

Sources of Sulphur

Sulphur Utilisation

Sulphur Production

Atmospheric Inversion (meteorology)

Normal atmospheric conditions

How and why inversions occur

Consequences

Methanogenesis

Methanogenesis is a form of anaerobic respiration that uses carbon as a electron acceptor and results in the production of methane.

Hydrolysis

Acidogenesis

Acetogenesis

Methanogenesis

Applications and Benefits of Environmental Biotechnology

What is Environmental Biotechnology?

Significance towards agriculture, food security, climate change mitigation and adaptation and the MDGs[edit]

Significance towards industrial biotechnology[edit]

Applications of Environmental Biotechnology

Nitrogen Removal

Removal Processes

Nitrification-Denitrification

Nitritation-Denitritation

Nitritation-Anammox

Disinfectants Chlorine Dioxide

Why is Chlorine Dioxide so good?

Applications

Microbial transformations of heavy metals

Enumerating Microorganisms

The Methods of Enumeration in Microbes

Direct/Viable

Indirect/Viable

Direct/Total

Indirect/Total

Types

Sequencing Batch Reactor Process Cycles

Anoxic Fill

Aerated Fill

React

Settle

Decant

Idle

Applications

Basic principles

Advantages

Disadvantage

Color coding

Waste Type

Classification

Colour Coding

Description

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