Friday, March 24, 2017

Methods of air pollution control - zoning, source correction

To effectively tackle the problem of air pollution, it is essential to prevent or minimize the formation of pollutants at the source.In case of industrial pollution, this can be achieved by analysing the process design amd selecting those methods that do not contribute to air pollution or have minimum impact due to air pollution. This technique is known as 'source correction methods'. The application of these methods is difficult, however some of these methods can be applied without having a major impact on economy of operation.
Below described are a few methods for control of pollution at source.
  1. Raw material change – When raw material causes air pollution, a purer grade of raw material may reduce generation of undesirable substances. 
    • An example in this regard is the use of low sulphur diesel in place of regular diesel which contains a higher sulphur content leading to effluents with a high concentration of sulphur particulates. 
    • Another example would be usage of natural gas in place of coal to reduce the generation of particulates (both suspended and respirable).
    • Desulphurization of fuel is an alternative, however it is expensive and poses technical problems. Another problem is lack of availability of better alternatives and the cost involved. 
    • Coal combustion can be carried out with least air pollution by coal gasification. Coal gasification can be carried out by destructive distillation of coal or gasification of coke residues of carbonization with steam. 
2.  Operational change

  • By causing all dust creating activities that are generated in a process to be effectively controlled and separated by effecting an operational change in the manufacturing industry
  • Moistening the dust thereby binding the dust is a time old method to prevent dust from spreading.

3.  Modification or replacement of process equipment – This involves use  of new or modified techniques to lower emission of atmospheric pollutants.

  • An effective method to control dust in industries is by casing all dust creating activities               and the dust generated can be effectively controlled and separated.

  • Moistening the powder in order to bind the dust is an old method prevent dust from                    spreading
  •      Examples are listed below:
    • Unburnt carbon monoxide (CO) and hydrocarbons (HCs) from cylinders of an automobile engine can be burnt by injecting air into the hot exhaust manifold of the engine.
    • Hydrocarbons (HCs) released into the atmosphere from petroleum storage tanks due to temperature changes, direct vapourization and displacement due to filling can be reduced by designing tanks with floating roof covers or pressurising the tanks.
    • Replacing the open hearth furnace by oxygen furnace in steel industries helps in reducing air pollution
    • Alternate power for automobiles (Ex: Hydrogen power, Solar power) in place of internal combustion engines that use fossil fuels will help in significant reduction of air pollution.
    • Air pollution due to industries can be reduced by proper maintenance of equipment, housekeeping and cleanliness of facilities helps reduce air pollution.
    • Ore handling operations result in emission of large quantities of dust. In steel industries, raw ore is replaced with sintered pelletized ore to reduce dust emissions and blast furnace “slips”
    4.   Effective operation of existing equipment
    • Preventing leakage around ducts, piping and valves by checking seals and gaskets regularly air pollution from industries can be minimized.
                                      METHODS OF AIR POLLUTION CONTROL – ZONING

    Air pollution control by zoning:
    The CPCB (Central Pollution Control Board) has developed a tool for environmental planning for proper siting of industries thereby reducing the risks due to pollution and protect the environment. The CPCB in consultation with the SPCBs (State Pollution Control Boards) has developed a zoning atlas for siting of industries based on environmental considerations, district-wise, through-out the country. The zoning atlas for siting of industrial zones, classifies the environment in a region and presents the pollution receiving potential of various locations along with possible alternate sites through easy-to-read maps. The objectives for preparing the zoning atlas are:
    1. To zone and classify regions
    2. To identify locations for siting of industries and
    3. To identify industries suitable for identified sites

    The zoning atlas considers only environmental aspects. The zoning atlas helps in stream-lining the decision-making process along with the following benefits:

    • It provides a ready-reckoner for best suitable site and relevant environmental information
    • It helps to make decisions that are simple, faster, realistic, transparent and reliable
    • It provides a basis for incorporating environmental aspects into land use planning
    • It helps to plan for cost effective pollution control measures and programs
    • It helps an entrepreneur save money, time, efforts and risk
    • Helps develop infrastructural facilities
    • It helps check additional pollution in areas already stressed with pollution
    • It ensures that pollution potential of an industry is compatible with local conditions
    • It ensures that industries with high pollution potential that are desirous to locate an industry in a high risk area adopts clean technologies so that generation of wastes is prevented or made compatible with the receiving environment.
    • Helps in creating awareness among people regarding type of industries and nature of pollution anticipated in their neighbourhood
    • In view of all the above mentioned issues, an EIA helps achieve sustainable development.

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