15.9 of wastes Wastes are produced in three

15.9 Strategies
to control Environmental Pollution:

The
strategies for controlling environmental pollution can be

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(i)                
Waste management i.e., reduction
of the waste and proper disposal, also recycling of materials and energy.

(ii)              
Adopting methods in day-to-day
life which results in the reduction of environmental pollution.

15.9.1 Waste
Management             

 Waste aaccumulation possess serious threat to the environment. The amount of waste
is increasing rapidly due to industrialisation and urbanisation. Proper
disposal of waste thus becomes
very essential. There is an urgent need for the waste
management so that clean environment can be available
for our next
generations.

Methods of safe disposal of wastes

Wastes
are produced in three forms, solid, liquid and gaseous. Safe disposal of waste vary
according to the nature of waste. The management of waste is given in the
following table 15.4.

Type of waste

Method of disposal

Solid waste

Segregation, compositing dumping, incineration

Liquid Waste

Drainage, Sewage or  effluent treatment before discharge

Gaseous Waste

Use of scrubbers, and electrostatic precipitators

Table 15.4
Waste Management

 

 

  15.9.2 Disposal of solid waste

 

 Segregation:

House hold wastes are collected in small bins, which are then transferred to common public bins by
private or municipal workers. From these common bins, they are collected and carried to
the disposable sites. At the
disposable  site, garbage are  sorted out and separated into biodegradable
and non biodegradable waste . Non biodegradable waste
likes plastic, glass, metal glass etc, are sent for
recycling. Biodegradable wastes are deposited in landfills and are converted
into compost.

 Dumping:

An average city resident produces
tons of waste every year. Several sites are located for quick dumping of waste
where waste is thrown in the open. It is the common and cheapest method of
disposing waste on land. Now a days, this method is improved and is called landfill. In a
landfill, the solid waste is spread in thin layers, each layer is solidified by
bulldozer before the next layer is deposited. After every three meters a layer
of clean earth is added and that is also solidified by bulldozer.

 Incineration:

Another method of solid waste disposal is incineration. It is an industrial process
designed to reduce unwanted materials to simple solid and gaseous residues by
burning of wastes at very high temperature by using iincinerators. Some incinerators
generate energy from the burning waste but releases harmful chemicals to air creating pollution..

Compositing:

This is
an effective method of solid waste disposal. The waste is not only disposed but
also made as manures. The waste is first segregated as biodegradable or
non-biodegradable. Biodegradable materials like paper, wood, leaves etc can be
decomposed are selected for composting. The biodegradable waste is layered in
such way that air can enter easily. A little water is added to the pile for
easy decomposition. The pile or heap is covered for few days so that heat and steam can
decompose the matter faster. After about three weeks it can be used as manure.
Non bio degradable materials like plastic and glass etc are not used in
composting.

Bio technique method of
rearing earthworm known as vermiculture
converts biodegradable solid waste into compost.

 

Recycling

The recycling method transforms waste
disposal into valuable resources. The Recycling of waste recovering materials
and energies is shown by the flow diagram.

 

Recycling
Mechanism

Waste

 

 

                    Mechanical recovery                                                Conversion
recovery

      Glass                     Metal               Paper                           Landfills                      Incineration

                                                                                                                        Separation

Organic fraction

 

                                                                                                      Material                               Energy

            Closed – loop               Open – loop                                                                                                                                                                               Animal feed                            Electricity

                                                                                                (compost)                                  (Fuel)

    

  In  the
mechanical recovery fractions, glass and paper are gathered can be reused .Two ways fcan be
adopted for reusing materials namely closed- loop recycling and open -loop
recycling

In closed –loop recycling, the
waste is recycled to produce an article of the same type. (Example: Newspaper
may be recycled into newspaper) and in open-loop recycling the waste is
recycled to produce an article of different type (Example: conversion of
newspapers into cellulose). The conversion recovery fraction is either buried
in the landfills or burnt in the incinerators . organic fraction is recycled to yield both
materials and energy.

Waste recycling

In our home we often face electricpower failure. We also see
piles of rotten garbage in
our streets. Latest technology has developed to
get rid of both these problems simultaneously.  After removing non-biodegradable substance metals, plastic, glass, paper etc, from garbage, it is mixed with water and then cultured with bacteria to produce methane, commonly known as biogas. Biogas is used to produce
electricity  The
remaining product is used as manure ,

    

 

 

 

 

15.9.2 Disposal of liquid waste

       Sewage (Waste water) treatment

Sewage is the liquid waste which includes industrial and house hold waste.
Sewage treatment involves the following stages.

      Stage
– 1:Preliminary process

                        Removal of
large solid waste and filtration of waste water through screens.

      Stage – 2:Settling process

                          Settling
of waste water in tanks. As a result solid sludge settles down while floating
oils and grease and the surface can be skimmed off. The safe disposal of sludge
is a problem. However it is dried and may be incinerated or dumped.

      Stage – 3: Biological treatment Process

                          Degradation
of organic matter present in waste water by microbial oxidation.

      Stage
– 4: Precipitation, Nitrogen stripping and chlorination

                          Finally various
chemicals method like precipitation, to remove phosphates, Nitrogen stripping
to remove ammonia and chlorination to disinfect microorganism is done to
improve the quality of waste water. The treated water is then finally
discharged into water resources like rivers, lakes etc. or reused again for
industrial purposes.

                          This sewage treatment
process is summarised as shown below.