Unit-4

Environment- Traditional & futuristic methods

Q1) Explain waste water treatment process.

A1)

Waste water treatment 

It is a process used to remove contaminants from wastewater or sewage and convert it into an effluent that can be returned to the water cycle with acceptable impact on the environment, or reused for various purposes.

Step 1: Screening and Pumping

The incoming wastewater passes through screening equipment where objects such as rags, wood fragments, plastics, and grease are removed. The material removed is washed and pressed and disposed of in a landfill. The screened wastewater is then pumped to the next step: grit removal.

Step 2: Grit Removal

In this step, heavy but fine material such as sand and gravel is removed from the wastewater. This material is also disposed of in a landfill.

Step 3: Primary Settling

The material, which will settle, but at a slower rate than step two, is taken out using large circular tanks called clarifiers. The settled material, called primary sludge, is pumped off the bottom and the wastewater exits the tank from the top. Floating debris such as grease is skimmed off the top and sent with the settled material to digesters. In this step, chemicals are also added to remove phosphorus.

Step 4: Aeration / Activated Sludge

In this step, the wastewater receives most of its treatment. Through biological degradation, the pollutants are consumed by microorganisms and transformed into cell tissue, water, and nitrogen. The biological activity occurring in this step is very similar to what occurs at the bottom of lakes and rivers, but in these areas the degradation takes years to accomplish.

Step 5: Secondary Settling

Large circular tanks called secondary clarifiers allow the treated wastewater to separate from the biology from the aeration tanks at this step, yielding an effluent, which is now over 90% treated. The biology (activated sludge) is continuously pumped from the bottom of the clarifiers and returned to the aeration tanks in step four.

Step 6: Filtration

The clarified effluent is polished in this step by filtering through 10 micron polyester media. The material captured on the surface of the disc filters is periodically backwashed and returned to the head of the plant for treatment.

Step 7: Disinfection

To assure the treated wastewater is virtually free of bacteria, ultraviolet disinfection is used after the filtration step. The ultraviolet treatment process kills remaining bacteria to levels within our discharge permit.

Step 8: Oxygen Uptake

The treated water, now in very stabilized high-quality state, is aerated if necessary to bring the dissolved oxygen up to permit level. After this step, the treated water passes through the effluent outfall where it joins the Oconomowoc River. The water discharged to the river must meet stringent requirements set by the DNR. Pollutant removal is maintained at 98% or greater.

Step 9: Sludge Treatment

The primary sludge pumped from the bottom of the primary clarifiers in step three, along with the continuous flow of waste activated sludge from the aeration / activated sludge process in step four, must be treated to reduce volume and produce a usable end product.

Q2) Explain the different methods of environmental conservation.

A2)

Environmental conservation is the practice of us humans saving the environment from the loss of species, and the destruction of the ecosystem, primarily due to pollution and human activities.

Methods of environmental conservation

1. Forest conservation: reforestation help in conserving the forests, which are responsible for trapping absorbing a huge amount of carbon dioxide from reaching the atmosphere.

2. Soil conservation: Soil conservation helps control erosions and improves the soil for agricultural purposes.

3. Recycling: We should learn to recycle everything we can for as long as it is possible. Glass, paper, plastic and even metals are reusable, and should not be thrown away after its original use. About 90% of all plastic bottles do not reach recycling units and this is unfortunate. They are not biodegradable and about 500 billion of them are used every year. Reusing these bottles, containers, bags and more will help in environmental conservation.

4. Reducing water consumption: Clean, fresh and safe water is precious and not easily available. It is therefore very crucial to save as much water as possible, and prevent water- pollution, otherwise, it will be scarce in years to come.

5. Control pollution: We should regularly maintain our cars and leave them at home for as much as it is possible a

Composting also avoids littering, and not only does it protect the environment, but is also a reliable source of natural manure. Avoid chemical fertilizers, herbicides, pesticides and insecticides that pollute the environment. We should control pollution in as much as it is possible, to conserve the environment

s they are a primary source of air pollution. Using rechargeable batteries helps the environment as we will not be prone to throwing them away once they are empty.

Q3) List any three reasons to understand the importance of conservation.

A3)

To protect wildlife

The most obvious reason for conservation is to protect wildlife and promote biodiversity. Protecting wildlife and preserving it for future generations also means that the animals we love don’t become a distant memory. And we can maintain a healthy and functional ecosystem.

Some species cannot survive outside of their own natural habitat without human intervention such as in zoos and aquariums. So the destruction of their natural habitats poses a real threat to their survival. Furthermore, species that migrate and inhabit more than one natural habitat are also vulnerable. So the preservation of these habitats helps to prevent the entire ecosystem being harmed.

As more and more species face extinction, the work being done to protect the wildlife that calls this planet home is becoming more and more important.

To protect the earth

It’s no secret that the future of our planet desperately needs to be safeguarded, with climate change already wreaking havoc on our natural environment. In order to preserve the earth for future generations, we not only need to reduce the amount of harm that human activities have on the environment but support the natural world as much as we can.

Nature itself is our biggest tool in the fight against global warming, and through conservation work, we can fully utilise nature’s contribution to the mitigation action that is needed to avoid a catastrophic increase in temperature.

Everything from tropical forests to our coastline has a part to play in the fight against climate change, as well as protecting our communities. So it’s important to do all that we can to protect them.

 For human health

One pretty big reason for conservation work that is talked about a little less often is the impact that it has on human health, both in terms of preventing the emergence of new diseases and the production of medicines that we rely upon. Having wild habitats for animals serves as barrier. It prevents emerging infectious diseases from jumping from animals to humans. Previously undisturbed habitats have been cleared to make way for humans and agriculture. This has brought wild and domestic animals together and helped to facilitate the jump of diseases to humans.

One such example is the Ebola outbreak. Ebola is a zoonosis (an animal disease that can jump to humans). It is believed that it most likely spread to humans from bats.

A lot of the medicines that we use are also derived from chemicals that are produced by animals or plants. So by protecting nature we also protect the lifesaving drugs we rely upon, including anti-cancer drugs.

Simply put, we cannot be healthy in an unhealthy environment. It is in our own best interests to preserve the natural world as much as we can. The exploitation of the natural world threatens our capacity to provide food and water for the people on earth. And things like pollution are directly harmful to human health.

Q4) What is sanitary land filling method? Explain in detail with neat sketch.

A4) In this method of disposal waste is carried and dumped into the low lying area under an engineered operation, designed and operated in an environmentally sound manner as not to cause any public nuisance or hazards to public health or safety.

In this method, the refuse is dumped and compacted in layers of about 0.5 m thickness, and after the days work when the depth of filling becomes about 1.5 m, it is covered by good earth of about 15 cm thickness. This cover of good earth is called the daily cover so it does not cause any public nuisance like scattering of wind-blown litter, and evolution of unpleasant odours and foul smells as may be caused by an ordinary dumping of refuse on land.

The filling of refuse is actually done in sanitary land filling by dividing the entire landfill area into smaller portions, called cells. These cells are initially filed with the daily compacted refuse of about 1.5m depth, after filling all cells with first lift the second lift is laid about 1.5m height and covered with good earth cover of about 0.15m depth, called the intermediate cover.

The process will continue till the top most lift is piled up, over which the final cover of good earth of about 0.6 m depth shall be laid and well compacted to prevent the rodents from burrowing into the surface. A cap system may also be installed over the top of the final cover.

Q5) Explain in detail: shredding and pulverisation.

A5) Shredding refers to the actions of cutting and tearing; whereas, pulverisation refers to the actions of crushing and grinding. Shredding and pulverising may help in reducing the overall volume of the original MSW, by as much as 40%. The shredding and pulverisation not only helps in reducing the volume of MSW, but also helps in changing the physical character of the waste, which becomes practically odourless and unattractive to the insects.

The pulverisation of MSW is usually achieved in a hammer mill, where the raw solid waste is cramped with a force, sufficient to crush or tear individual components of the waste. The mill helps to produce a uniform or homogeneous mass of solid waste.

In order to further reduce the waste volume, and facilitate handling of the pulverised MSW, it is usually compacted to rectangular blocks or bails. The pulverised MSW is converted into bails by compacting the pulverised MSW under high pressures (of about 700 kPa) in either vertical or horizontal presses. This process is called bailing of MSW.

Volume reduction due to pulverising and bailing together, may occur by as much as 90% of the original waste volume.

The bailing process, thus, has significant advantages in decreasing the waste volume, and in providing an easy way for handling waste as blocks rather than as litter, thereby reducing the litter nuisance of scattering etc.

Q6) Explain in detail: major air pollutants along with its sources and effects.

A6) The atmospheric air may contain hundreds of air pollutants from the natural or the anthropogenic (manmade) sources.

PRIMARY POLLUTANTS

All these pollutants which are emitted directly from the identifiable sources either from the natural hazardous events like dust storms, volcanoes etc or from human activities like burning of wood, coal, oil in homes or industries etc are called the primary pollutants .

The following five primary pollutants contribute to about 90% of the global air pollution:

1. Oxides of sulphur particularly the sulphur dioxide (SO2)

2. Oxides of carbon particularly carbon monoxide (CO)

3. Oxides of nitrogen expressed as NOx

4. Volatile organic compounds (VOC), mostly hydrocarbons

5. Suspended particulate matter (SPM)

Less important primary pollutants are hydrogen sulphide (H2S), hydrogen fluoride (H2F) and other fluorides: methyl and ethyl mercaptans etc, which are usually rarely found in our general atmosphere, although if present, may prove quite harmful.

SECONDARY POLLUTANTS

These primary pollutants often react with one another or with water vapour, aided and abetted by the sunlight to form entirely a new set of pollutants, called the secondary pollutants. These new pollutants are often more harmful than the original basic chemicals that produce them.

Important secondary air pollutants are

1. Sulphuric acid (H2SO4)

2. Ozone (O3)

3. Formaldehydes

4. peroxy-acyl-nitrate (PAN)

Characteristics: solid particles like dust, smoke and fumes: liquid particles like mist and fog.

Source: dust storms, cigarette smoke, smoke from burning of garbage and fossil fuels, and fumes like those of zinc or lead etc.

Effects: effects on respiratory and breathing system, aggrevation of existing respiratory and cardiovascular diseases, alteration of body’s defence systems against foreign materials, damage to lung tissues, carcinogenic effects and premature mortality.

Characteristics: colourless gas, taste threshold at 0.3 ppm and odour threshold at about 0.5 ppm.

Source: combustion of oil and coal in power stations or automobiles.

Effects: effects on breathing, respiratory illness, breakdown of lung defences. Asthmatics and those suffering from chronic lung and cardiovascular diseases are sensitive to SO2 exposures. It may lead to photochemical smog in some areas by oxidising the hydrocarbons.

Characteristics: colourless, tasteless, odourless gas at atmospheric concentrations.

Sources: incomplete combustion of coal and oil etc.

Effects: at elevated concentrations, CO impairs visual perception, manual dexterity and mental ability. Under short term exposure it causes drowsiness and headaches. It also leads to formation of photochemical smog in some areas.

Characteristics: NO is a reddish brown highly reactive gas. Odour threshold is at 0.2 ppm.

Sources: high temperature combustion in automobiles and to some extent in thermal power stations.

Effects: NO plays a major role in tropospheric ozone formation.

NO2 irritates the lungs, causes bronchitis and pneumonia, lowers resistance to respiratory infections.

Characteristics: colourless gas. Threshold odour is at about 0.3 ppm.

Sources: a secondary air pollutant produced by photochemical pollution, being the largest constituent of photochemical smog along with PAN etc.

Effects: ozone reduces lung function, and is associated with cough, sneezing, chest pain. It may affect all health people as well as the people with impaired respiratory systems.

Q7) What is global warming? And what are its causes?

A7) Global warming occurs when carbon dioxide (CO2) and other air pollutants and greenhouse gases collect in the atmosphere and absorb sunlight and solar radiation that have bounced off the earth’s surface. Normally, this radiation would escape into space—but these pollutants, which can last for years to centuries in the atmosphere, trap the heat and cause the planet to get hotter. That's what's known as the greenhouse effect.

The continuous excessive burning of fossil fuels and large scale deforestation by humans has increased the carbon dioxide gas in the atmosphere. And carbon dioxide is considered to be the major green house gas as it responsible for about 60% of the total green house gases.

Green house gases in the lower atmosphere act like the glass of a green house trapping the heat as it radiates back from the earth into the space.

Q8) What is the methodology for preparing EIA?

A8) EIA essentially involves three steps

1. Impact identification: it may be carried out with the help of checklists, metrics or networks. Checklists merely present a list of environmental parameters to be investigated for possible impacts. Metrices are two dimensional checklists in which cause-effect relationships are established by listing possible project activities along one axis and potentially impacted environmental characteristics. Networks illustrate cause-condition effect linkages as also temporal dimensions, and therefore provide the most comprehensive methodology for impact identification.

2. Prediction of environmental impacts: it requires the greatest degree of scientific application. This step involves projecting the baseline environmental settings into the future, with a nd without the project and then performing the necessary calculations for predicting real impacts of the proposed development.

3. The evaluation of impacts: the evaluation of impacts in an EIA calls for conservation of the predicted values for some various environmental parameters to a comparable set of units using some system of normalisation.

Q9) Explain EMP.

A9)

A detailed environmental management planning has to be drawn and submitted with EIA for formulation, implementation and monitoring of the environmental protect measures, during and commissioning of the proposed project..

The EMP for commissioning of the plant will ensure that resources are used with maximum efficiency to minimise generation of wastes, by adequately treating the residuals, recovering by-products and adopting recycling techniques to the maximum possible extent.

Q10) What are environmental metrics?

A10) Environmental metrics are designed to assess the environmental impact of technology or activity. Such impacts are primarily related to using natural resources (lifecycle INPUTS) and generating waste and emissions (lifecycle OUTPUTS). The ultimate sustainability goal is to minimize the environmental impacts due to using non-renewable resources and minimizing waste and pollution. Since the complete elimination of these impacts is hardly possible (any technology has its environmental costs!), it is also important to evaluate the rate at which environment can absorb the impacts and become remediated.

Examples of environmental metrics are

Water use, land use, embodied energy, Eutrophication potential (EP), global warming potential (GWP) etc.