Control of Air Pollution || Learns Biology

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Control of Air Pollution

Important preventive strategies to control air pollution are

(i) Selection of suitable fuel (eg., fuel with low sulphur content) and its efficient utilisation to reduce pollutant level,

(ii) Use of eco-friendly equipments and modified industrial processes to reduce emissions.

(iii) Correct selection of manufacturing site and zoning for industrial set-up to disperse pollution sources.

The most common methods of eliminating or reducing pollutants to an acceptable level include destroying the pollutant by thermal or catalytic combustion, changing the pollutant to a less toxic form, or collecting the pollutant by use of equipment to prevent its escape into the atmosphere.

Control of Particulate Matter

To control particulate matter, two important devices may be used

(i) Arresters-These selectively trap the particulate material from the contaminate
air. Arresters are of different typesCyclonic separalors and trajectoy separators are
commonly used to separate out particulate matters from industrial emissions
With minimum moisture content. These separators work on the principle of dust
Separation by centrifugal force and are efficient for coarser dust particles.

(ii) Serubbers-These are used to clean air for both dusts and gases. T hese may be dry Or wet. Both dry and wet type scrubbers are used for dust separauon. SCTubber 1s best suited device for the removal of gaseous pollutants.

Control of Gaseous Gaseous Pollutants

aseous pollutants can be controlled mainly by three processes-combustion, absorption and adsorption.

In conbustion, oxidisable gaseous pollutants are completely burnt at a high temperature. Petro-chemical, fertiliser. paints and varnish industries use combustion control of gaseous pollutants.

In absorption technique, gaseous pollutants are absorbed in suitable absorbent materials.

In adsorption technique a good and appropriate adsorbing substance is used to control toxic gases, vapours and inflammable compounds.

Control of Automobile Exhaust

MPFI (Multi-point fuel injection) engines significantly reduce the unburnt hydrocarbons in the automobile exhaust.

Catalytic converter filter can convert nitrogen oxides to nitrogen.

Good quality, unleaded fuel should be used.

CNG (Compressed natural gas) based automobile engines aso reduce the pollutants in exhaust.

Barium compounds should be added to the fuel to reduce the amount of exhaust gases.

Traffic should be controlled.

WATER POLLUTION

Physical and chemical characters of water are changed due to addition of organ and inorganic substances and organisms to water. These changes are harmful tor the health and thus reduce the usefulness of water.

The main water polluting agents are listed below.

Sources of Water Pollution

The sources of water pollution are mainly of two types

(a) Point sources: These sources have a fixed location and discharge the pled from this location. Example-Outlet of a factory. These sources can De in effective manner

(b) Non-point source: In this case, the sources have no fix locatot Agriculture runoff, city storm water flow etc. These sources are difficult to control.

Water Pollutants

Main water pollutants are household detergents, Sewage and other wastes, Agricultural wastes, Release from nuclear reactors, etc. These pollutants can wastes, dly be divided into following main categories

Biological pollutants: These include pathogens, like bacteria and viruses.

Chemical pollutants: Organic chemicals like biocides, polychlorinated biphenyles (PCBs), 1norganic compounds like phosphates, nitrates, Iluorides, heavy metal like arsenic, cadmium, chrOmium, mercury and lead etc.

Physical pollutants: These include oil spills, hot water etc. Some of the important pollutants can be described below

(a) Municipal Waste and Sewage

Municipal waste and sewage contains human and animal excreta, food residues, domestic wastes, soaps, detergents, etc. It is always rich in bacteria and organic substances.
Some otlher components may also be present in sewage. These depend upon tume and
space.

Household detergents are one of the major causes of water pollution. These are used for washing clothes and cleaning utensils in almost all the houses. These are released into drains which ultimately carry them to water reservoirs like lake, rivers, etc. The water becomes polluted.

Constituents

The major part of the municipal waste consists of organic matter, detergents
and biological pollutants.

Besides this, organic phosphatee releases inorganic phosphate which acts as nutrient Nitrogen 1s present as ammonical nitrogen. The other pollutants heavy metals, cyanide, oil, etc.

The major constituents of detergents include compounds of phosphate, nitrate
and ammonium and alkyl benzene sulphonate (ABS).

Effects

Water reservoirs always maintain a balance between available oxygen and decomposition of organic matter. This capacity is lost due to addition of excessive sewage and other wastes.

Alkyl benzene sulphonate (ABS), generally forms foam on water surface. abs is non-biodegradable and thus accumulates in water reservOirs. Higher Concentrations of ABS cause obstruction to aquatic organisms. The recycling and self-regulation of the system is disturbed.

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