Environmental Science and Engineering-GE 2021

Unit-IIEnvironmental Pollution

Dr. V.Nagarajan

UNIT II ENVIRONMENTAL POLLUTION

Definition – causes, effects and control measures of: (a) Air pollution (b) Water pollution (c) Soil pollution (d) Marine pollution (e) Noise pollution (f) Thermal pollution (g) Nuclear hazards Soil waste management: causes, effects and control measures of municipal solid wastes – role of an individual in prevention of pollution – pollution case studies – disaster management: floods,earthquake, cyclone and landslides.

Field study of local polluted site – Urban / Rural / Industrial / Agricultural.

THERMAL POLLUTIONThermal pollution can be defined as presence of waste heat in the water which can cause undesirable changes in the natural environment.Causes of thermal pollution:

• Heat producing industries i.e.,thermal power plants, nuclear power plants, refineries, steel mills etc. are the major sources of thermal pollution.

• Power plants utilize only 1/3 of the energy provided by fossil fuels for their operations.Remaining 2/3 is generally lost in the form of heat to the water used for cooling.

• Cold water, generally, is drawn from some nearby water-body, passed through the plant and returned to the same water body, with temperature 10-16°C higher than the initial temperature.

• Excess of heat reaching such water bodies causes thermal pollution of water.

Effects of Thermal Pollution1. The dissolved oxygen content of water is decreased as the

solubility of oxygen in water is decreased at high temperature.2. High temperature becomes a barrier for oxygen penetration into

deep cold waters.

THERMAL POLLUTIONEffects of Thermal Pollution

3. Toxicity of pesticides, detergents and chemicals in the effluents increases with increase in temperature.

1. The composition of flora and fauna changes because the species sensitive to increased temperature due to thermal shock will be replaced by temperature tolerant species.

2. Metabolic activities of aquatic organisms increase at high temperature and require more oxygen, whereas oxygen level falls under thermal pollution.

3. Discharge of heated water near the shores can disturb spawning and can even kill young fishes.

4. Fish migration is affected due to formation of various thermal zones.

THERMAL POLLUTIONControl of Thermal Pollution

The following methods can be employed for control of thermalpollution:(i)Cooling ponds,(ii) Spray Ponds,(iii) Cooling towers

(i)Cooling Ponds:

Water from condensers is stored in ponds where natural evaporation cools the water which can then be recirculated or discharged in nearby water body.

(ii) Spray Ponds: The water from condensers is received in spray ponds. Here the

water is sprayed through nozzles where fine droplets are formed. Heat from these fine droplets is dissipated to the atmosphere.

(iii) Cooling Towers:(a)Wet cooling tower:

• Hot water is sprayed over baffles. • Cool air entering from sides takes away the heat and

cools the water.• This cool water can be recycled or discharged.• Large amount of water is lost through evaporation and

in the vicinity of wet cooling tower extensive fog is formed which is not good for environment and causes damage to vegetation.

(b) Dry cooling tower:

• The heated water flows in a system of pipes. • Air is passed over these hot pipes with fans. • There is no water loss in this method but installation

and operation cost of dry cooling tower is many times higher than wet cooling tower.

Soil Pollution• Soil is the upper layer of earth’s crust which is formed by weathering of

rocks.

• Organic matter in the soil makes it suitable for living organisms.

• Soil pollution is defined as the build-up in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease causing agents, which have adverse effects on plant growth and animal health.

• Dumping of domestic and industrial wastes causes soil pollution.

There are many different ways that soil can become polluted, such as:

• Seepage from a landfill

• Discharge of industrial waste into the soil

• Percolation of contaminated water into the soil

• Rupture of underground storage tanks

• Excess application of pesticides, herbicides or fertilizer

• Solid waste seepage

Soil Pollution• The most common chemicals involved in causing soil pollution are:

• • Petroleum hydrocarbons

• • Heavy metals

• • Pesticides

• • Solvents

Types of Soil Pollution

• Agricultural Soil Pollutioni) pollution of surface soilii) pollution of underground soil

• Soil pollution by industrial effluents and solid wastes

i) pollution of surface soil

ii) disturbances in soil profile

• Pollution due to urban activities

i) pollution of surface soil

ii) pollution of underground soil

Causes of Soil Pollution:

• Polluted water discharged from factories

• Runoff from pollutants (paint, chemicals, rotting organic material) leaching out of landfill

• Oil and petroleum leaks from vehicles washed off the road by the rain into the surrounding habitat

• Chemical fertilizer runoff from farms and crops

• Acid rain (fumes from factories mixing with rain)

• Sewage discharged into rivers instead of being treated properly

• Over application of pesticides and fertilizers

• Purposeful injection into groundwater as a disposal method

• Interconnections between aquifers during drilling (poor technique)

• Septic tank seepage

• Lagoon seepage

• Sanitary/hazardous landfill seepage

• Cemeteries

• Scrap yards (waste oil and chemical drainage)

• Leaks from sanitary sewers

Effects of Soil Pollution

• Agriculturalo Reduced soil fertilityo Reduced nitrogen fixationo Increased erodibilityo Larger loss of soil and nutrientso Deposition of silt in tanks and reservoirso Reduced crop yieldo Imbalance in soil fauna and flora

• Industrial• Dangerous chemicals entering underground water• Ecological imbalance• Release of pollutant gases• Release of radioactive rays causing health problems• Increased salinity• Reduced vegetation

• Urban

• Clogging of drains

• Inundation of areas

• Public health problems

• Pollution of drinking water sources

• Foul smell and release of gases

• Waste management problems

• Effects of soil pollution in general:• pollution runs off into rivers and kills the fish, plants and other aquatic life

• crops and fodder grown on polluted soil may pass the pollutants on to the consumers

• polluted soil may no longer grow crops and fodder

• Soil structure is damaged (clay ionic structure impaired)

• corrosion of foundations and pipelines

• impairs soil stability

• may release vapours and hydrocarbon into buildings and cellars

• may create toxic dusts

• may poison children playing in the area

Control of soil pollution• Adopt the three R's: Reduce, Reuse, and Recycle

• Reducing chemical fertilizer and pesticide use o Applying bio-fertilizers and manures can reduce chemical fertilizer

and pesticide use.o Biological methods of pest control can also reduce the use of

pesticides and thereby minimize soil pollution.

• Reusing of materials

• Materials such as glass containers, plastic bags, paper, cloth etc. can be reused at domestic levels rather than being disposed, reducing solid waste pollution.

• Recycling and recovery of materialso Materials such as paper, some kinds of plastics and glass can and are

being recycled. o This decreases the volume of refuse and helps in the conservation of

natural resources.o For example, recovery of one tonne of paper can save 17 trees.

• Reforestingo Control of land loss and soil erosion can be attempted through restoring

forest and grass cover to check wastelands, soil erosion and floods. o Crop rotation or mixed cropping can improve the fertility of the land.

• Solid waste treatment o Proper methods should be adopted for management of solid waste

disposal. o Industrial wastes can be treated physically, chemically and biologically

until they are less hazardous.o Acidic and alkaline wastes should be first neutralized; the insoluble

material if biodegradable should be allowed to degrade under controlled conditions before being disposed.

o As a last resort, new areas for storage of hazardous waste should be investigated such as deep well injection and more secure landfills.

o Burying the waste in locations situated away from residential areas is the simplest and most widely used technique of solid waste management.

• Solid waste treatment o Incineration of other wastes is expensive and leaves a huge residue and

adds to air pollution.o Pyrolysis is a process of combustion in absence of oxygen or the material

burnt under controlled atmosphere of oxygen. It is an alternative to incineration. The gas and liquid thus obtained can be used as fuels.

o Pyrolysis of carbonaceous wastes like firewood, coconut, palm waste, corn combs, cashew shell, rice husk paddy straw and saw dust, yields charcoal along with products like tar, methyl alcohol, acetic acid, acetone and a fuel gas.

• Natural land pollution:o Land pollution occurs massively during earth quakes, land slides,

hurricanes and floods. o All cause hard to clean mess, which is expensive to clean , and may

sometimes take years to restore the affected area.o These kinds of natural disasters are not only a problem in that they

cause pollution but also because they leave many victims homeless.

Marine Pollution is defined as the direct or indirect introduction by humans of substances or energy into the environment (including estuaries), resulting in harm to living resources, hazards to human health, hindrances to marine activities including fishing, impairment of the quality of sea water and reduction of amenities.

Causes / Sources of Marine Pollution:The main sources of marine pollution are:

(i)rivers, which bring pollutants from their drainage basins,

(ii)Catchment area i.e. coastline where human settlements in the form of

hotels, industry, agricultural practices have been established, and

(iii)oil drilling and shipment .

Marine Pollution

The origin of various sources of pollution are listed below :

Marine Pollution

Source Percentage

Land 45

Air 33

Transportation 12

Dumping 9

Offshore 1

• DredgingAmong all land based activities that cause marine

pollution, dredging of ports and harbours is probably the most significant in terms of propagation of pollutants.

The process of dredging causes the disruption of bottom sediments.

Toxic materials released from the disturbed soils may go into solution and cause severe mortality to marine

estuarine life.

Re-deposition of suspended materials could possibly eliminate bottom flora & fauna.

Organic material in the suspended material may deplete available oxygen in the surrounding waters and can

create temporary stress conditions for aquatic animals.

Marine Pollution

• DredgingIf suspended sediments are sufficiently concentrated, penetration of light in the water column is significantly reduced, thereby causing damage to light depending photosynthetic algae, corals and other aquatic organisms.

Explosives used to break rock formations destroy bottom habitats.

Pressure radiation due to blasting, often injure or disable marine life at considerable distances.

Areas of sediment depositions, typically contain fine grained sand which act as "sinks" for many compounds.

Many organic contaminants have a low solubility in water and therefore are associated with suspended solids and

are transported along with the sediments.

Marine Pollution

• DredgingMitigation measures:

The problem of dredged material disposal can be considerably reduced, if effluents from land based

sources are controlled.

Further to control/ limit the propagation of contaminants can be achieved by proper selection of dredging process,

equipment and disposal sites.

Another mitigative measure is to avoid or minimise dredging during fish migration, breeding and spawning seasons.

Marine Pollution

• DredgingIn areas where, chemical contaminants of the bottom sediments exceed threshold values, selection of

appropriate dredging equipment is to be considered.

These include:*

Oozer pump suction dredger to avoid the release of material at the point of excavation*

Closed clamshell bucket dredger or trailing cutter suction dredger with no overflow

*Proper offloading equipment on a disposal barge to pump

to disposal sites without leakage

Marine Pollution

Ship discharges include :* Ballast water from cargo tanks / oil tankers. Tank washings from oil tankers. Bilge waste from machinery spaces. Residues from fuel & lubricating oil purification units, spent

lubricating oils, and sludge from tankers. Sanitary wastes. Garbage

Although many large ships have sewage treatment, and oil/water separation facilities, smaller ships and other port crafts lack these facilities.

To mitigate this problem all ports must have connections from ship to shore-based facilities to receive and treat sanitary wastes, oily waste & garbage.

For vessels anchored outside port, a floating reception facility such as towed or self propelled barge may be considered.

Marine Pollution

Ballast Water Discharges: Discharge of ballast water in ports may result in coliform & pathogens from the port of origin to propagate to the port of destination.

Increases in ship speeds, especially those of container vessels, have resulted in increase of survival rates of these pathogens.

It is mandatory for ships to exchange their ballast water several times in course of their voyage.

Oil Spills - Detection and Cleanup:Although major oil spills constitute an estimated two-percent of the total marine pollution, they cause in addition to environmental damage, a serious aesthetic degradation of the shoreline. The major causes of the spill are :

Marine Pollution

Spills - Detection and Cleanup: *

Marine causalities such as collisions, grounding, fires, etc.*

Hull failure*

Failure of equipment such as pipelines, flanges, hoses, etc.*

Incorrect operating procedures

The avoidance of spill is a key requirement. All ports must have an emergency contingency plan clearly

outlining authority and responsibility for dealing with such situations.

A mechanism for alerting and reporting must be established. Oil spill clean up equipment must be available with all ports to

deal with minor to medium spills.

Marine Pollution

Spills - Detection and Cleanup:

These equipments must include containment booms, recovery equipment and suitable dispersants.

All operators should be trained to handle the equipment. These equipments should be routinely checked and regular

exercises must take place to test the efficiency reporting, alerting and operating mechanisms.

Marine Pollution

Containment and skimming -to clean up the slick.Sorbents -- large sponges that absorb the oil from the water. In situ burning.Dispersants- chemicals which break down oil much more

quickly than the elements can alone.

Marine Pollution

Effects of Oil on Marine ecosystems mainly depend on the following factors:

Type of Oil (crude or refined)Amount releasedDistance of release from shoreTime of yearWeather conditionsAverage water temperatureOcean currents

Anti-Fouling Paints: By their very nature anti-fouling paints inhibit the growth and/or destroy a wide variety of marine organisms.

Severe damage to the aquatic life is caused by the application of paints containing tri-butyl-tin.

Careless application of this paint causes more damage than necessary.

Removal of old paint from vessels and floating craft in the waterfront also causes similar damage.

New ship building/repair facilities should be located where marine life is minimal.

Marine Pollution

Run-Off from raw material storage: Raw materials such as coal, mineral ores, sulphur, salt, etc, are

usually stored in the open in port areas prior to loading or after unloading from ships.

Due to their large volumes, it is uneconomical to store them otherwise.

Due to prevalent weather conditions such as rain and wind, frequently, significant amounts of these materials find themselves in harbour waters.

Over a period of time, enormous quantities are built up to such levels that cause acute toxicity and fatalities to aquatic life.

To alleviate this problem, bunds are to be built along the periphery of the storage areas along with suitable drains.

These drains may flow to a centralised location, where water can be treated before disposal to harbour waters.

Marine Pollution

Water front discharge: Most port jetties are designed so that they have slight slope

towards the harbour waters, to avoid flooding and/or water stagnation due to heavy rainfall.

Inadvertently, this type of jetty design allows unimpeded flow of contaminants into harbour waters.

The principal constituents of these contaminants are oils, diesel, hydraulic oils, and spillages of cargo on the wharf.

As far as possible, direct drainage from the wharves and piers must be avoided.

These areas are to be paved and sloped so that they direct flows to catch basins, where the water collected is treated before disposal.

Marine Pollution

EFFECTS OF MARINE POLLUTION

1) Untreated or partially treated sewage effluent, or organically rich industrial effluent such as that from fish processing plants, present a number of problems.

* Decomposition of organic matter causes a drop in dissolved oxygen, particularly in calm weather and sheltered bays. This can cause the death of marine plants and animals, and may lead to changes in biodiversity.

* Effluent, rich in nitrogen and phosphorus, results in `eutrophication' (overfertilization), which may cause algal blooms. These blooms can discolour the water, clog fish gills, or even be toxic, e.g. red tides. Microbial breakdown of dead algae can cause oxygen deficiencies.

* Pathogenic microorganisms cause gastric and ear-nose- throat infections, hepatitis, and even cholera and typhoid. Filter feeding animals (e.g. mussels, clams, oysters) concentrate pathogens in their gut, so eating shellfish from polluted waters is a health risk.

* Effects from industrial discharges are generally limited to the area next to the discharge (the `mixing zone'). Water quality guidelines specify maximum levels of pollutants allowed in the receiving water.

2) Oil spills smother plants and animals, preventing respiration. In seabirds and mammals it can cause a breakdown in their thermal insulation. Chemical toxicity can cause behavioral changes, physiological damage, or impair reproduction. Oil pollution is an eyesore, and cleanup and subsequent disposal of oily wastes is difficult.

3) Pesticides, such as DDT, and other persistent chemicals e.g. PCBs, accumulate in the fatty tissue of animals. These chemicals can cause reproductive failure in marine mammals and birds.

4) Ships often paint their hulls with anti-fouling substances, e.g. tributyl-tin or TBT, to prevent growth of marine organisms. These substances leach into water and, in high traffic areas such as harbours and marinas, can affect animal life. There is a world wide trend towards limiting the use of TBT containing paints.

5) Plastics kill many marine animals. Turtles, for example, often swallow floating plastic bags, mistaking them for jelly- fish. Animals are often strangled when they become entangled with plastic debris.

Control of Marine Pollution(i) Toxic pollutants from industries and sewage treatment

plants should not be discharged in coastal waters. (ii) Run off from non-point sources should be prevented to

reach coastal areas.(iii) Sewer overflows should be prevented by having separate sewer and rain water pipes.(iv) Dumping of toxic, hazardous wastes and sewage sludge should be banned.(v) Developmental activities on coastal areas should be minimized.(vi) Oil and grease from service stations should be processed for reuse.(vii) Oil ballast should not be dumped into sea.(viii) Ecologically sensitive coastal areas should be protected by not allowing drilling.