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SOLID WASTE AND ITS MANAGEMENT

MD MOUDUD HASAN LECTURER

DEPARTMENT OF AGRICULTURAL AND INDUSTRIAL ENGINEERINGFACULTY OF ENGINEERING

HAJEE MOHAMMAD DANESH SCIENCE AND TECHNOLOGY UNIVERSITYDINAJPUR

2Solid Waste

“The waste materials which have been rejected for further use and which can neither readily escape into the atmosphere nor can be transported by water into streams are called as solid waste.”

3The Types and Sources of Solid Wastes Municipal Wastes These include garbage (i.e. biodegradable food waste);

Rubbish (i.e. non-biodegradable solid waste from homes, offices, markets, hotels, etc.);

Construction and demolition wastes: Sludges from septic tanks; wires; conduits pipes; ashes; abandoned vehicles etc.

Special Wastes These include hazardous wastes like toxic substances

(pesticides, heavy metal sludges); Radioactive wastes; Biological waste; explosives, inflammable substances, corrosive materials, etc.

4The Types and Sources of Solid WastesDomestic WastesThese include wastes generated from domestic

cooking and serving of food. Examples Garbage, waste paper, plastic, cloth etc.

Agricultural WastesThese wastes result from farms, feed lots and live-

stock yards. Examples Corn residues, baggasse from sugarcane manures, paddy husk, etc.

5The Types and Sources of Solid Wastes Industrial WastesThese include (a) Process wastes: Here waste depends on the

products being manufactured. Examples Plastic wastes, rubber wastes, metal scraps, food-processing wastes, etc.

(b) Non-process wastes: Here waste is common to all industries. Examples Office and cafeteria wastes, packing wastes, etc.

6Causes of Generation of Solid Wastes (i) Over-population: Solid waste generated per person multiplied

by total population results in increased generation of solid waste every day.

(ii) Urbanization: Urbanization requires various construction activities like construction of buildings, markets, shopping malls, roads, railways, airports, bridges, dams, water supply and sewage disposal systems. Each construction activity also generates solid wastes.

(iii) Affluence: Consumers with high purchasing capacity discard ‘obsolete goods’. This leads to solid waste generation.

(iv) Advances in Technology: These lead to large scale production of goods for consumption based society preferring disposable items and almost every item ‘packaged’. All these result in generation of huge quantities of solid wastes.

7Effects of Solid Wastes The accumulation and improper handling of the solid wastes results in various

health and environmental hazards. Some of these effects are described below: (i) Flies and mosquitoes breed on the choked drains and gully pits through

solid wastes. These flies and mosquitoes than contaminate food and water. In turn, diseases like diarrhoea, amoebic dysentery, bacillary dysentery, malaria, dengue, etc. results.

(ii) The stray animals and scavengers invade the garbage dumps of roadside. It results in harming the aesthetic beauty of the surroundings.

(iii) Bad odours pollute the air as a result of decomposition of organic solid wastes.

(iv) Percolation of decomposed garbage cause pollution of underground water and land. The crops and water supply gets contaminated and result in cholera, hepatitis, jaundice, gastro-intestinal diseases.

(v) Rats living in solid waste dumping sites rapidly multiply in numbers and may cause plague and other diseases.

8Solid Waste Management Important solid waste management practices are briefly

described below: (i) Source Reduction: It involves changing the design,

manufacture, or use of products and materials to reduce the amounts of solid waste generation. Examples: Two-sided copying of paper, backyard composting, etc.

(ii) Recycling: From the waste stream; paper/glass/plastic/metal etc. are sorted, collected, processed and then manufactured, sold and purchased as new products. Advantages: Energy saving, prevention of emission of many

greenhouse gases/water pollutants, job creation, resource conservation for future and reduced need of new land fills and incinerators.

9Solid Waste Management(iii) Treatment: Suitable treatment is given depending on

the nature of solid wastes. (iv) Disposal: Solid wastes can be disposed in combustion

facilities and land fills.The most preferred method for solid waste management

is source reduction (including reuse). It is followed by recycling and composting. Lastly, disposal of solid waste is done.

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11Solid Waste Disposal The various method commonly employed for disposal of solid waste

are explained below: Composting Composting is the thermophilic and aerobic decomposition of

organic matter present in solid waste by microorganisms, mainly bacteria and fungi. As a result of this composting process, the organic matter is transformed into a stable humus like substance, which is a valuable manure for crops.

(i) Classification of composting techniques based on oxygen use: (a) Aerobic composting: It requires high temperature and result in

rapid decomposition of organic matter. Odours are also absent. (b) Anaerobic composting: It requires low temperatures.

Decomposition of organic matter of solid waste is slow. It needs minimum attention.

12Solid Waste Disposal(ii) Vermicomposting It uses a special kind of earthworm and a container of food

scraps. After some time, the food is replaced with worm droppings, a rich brown matter that serves as excellent natural plant food.

The advantages of vermicomposting over conventional composting: Vermicomposting needs less space than normal composting. Vermicomposting is ideal for apartments in high density urban areas. Vermicomposting provides excellent natural plant food.

13Solid Waste Disposal Illegal Dumping/Open Dumping/Fly Dumping/Midnight Dumping It is the disposal of solid waste by dumping in open areas, dumped from

vehicles along roadsides, and/or dumped late at night. Advantages:

It is done to avoid either the time and effort required for proper disposal or to avoid disposal fees.

Disadvantages: (i) Illegal dumping of non-hazardons wastes often attract more waste, even

the hazardous wastes. (ii) Illegal dump sites divert land from more productive uses. (iii) Property values decrease as a result of illegal dumping. (iv) Public nuisance is created by illegal dump sites.

14Solid Waste Disposal Land Dumping Solid wastes are dumped in low-lying areas outside the city/town

limits. These areas have no provision of leachate collection and treatment. Moreover, land fill gas is neither collected nor used.

Advantages: (i) It requires no planning. (ii) It is cheaper.

Disadvantages: (i) The waste is untreated, uncovered and not segregated. It is the

breeding ground for flies, other insects, rats etc. that spread diseases. (ii) Rainwater run-off from these dump sites contaminate nearby land and

water there by spreading diseases.

15Solid Waste Disposal Landfills Landfill site is a pit that is dug in the ground. The solid waste is

dumped and the pit is covered with a layer of soil to form a cell. The process is repeated every day so that many cells completely fill the landfill site. Finally, about 1 m of earth layer covering is done.

Advantages: (i) Breeding of insects is prevented. (ii) Landfill sites can be developed as a park or a parking space.

Disadvantages: (i) All types of wastes are dumped in land fill sites without segregation.

When rainwater seeps through them, it gets contaminated and in turn pollutes the surrounding area, and ground water.

16Solid Waste Disposal Sanitary Landfills Sanitary landfill sites have liner systems and other safeguards to

prevent ground water contamination. These sites are consistent with the economic considerations, hydrogeological requirements, climatic conditions and topography.

Advantages: (i) The site is well above the ground water table, so underground water

pollution is avoided. (ii) The site is easily accessible so process is low in cost. (iii) The site is atleast 1.5 km down wind from the commercial and

residential areas so it is not offensive to the surrounding environment. (iv) The finished sanitary landfill can be used for the development of

regions of recreation like parks, golf-courses etc.

17Solid Waste DisposalSanitary LandfillsDisadvantages:

(i) Leachate from sanitary landfill site can contaminate the ground water.

(ii) The sites cannot be used in future as a productive farm land. (iii) In a sanitary landfill, about 60% of the methane gas (odourless)

is generated. When its concentration in air reaches about 5%, it is explosive and so very hazardous.

(iv) Aesthetic problems may arise as a result of poorly operated landfill operations.

18Solid Waste Disposal Combustion Solid waste is burned at high temperature in combustion

facilities. Advantages:

(i) Energy is generated. (ii) Amount of waste is reduced by up to 90% in volume and 75% in

weight. Disadvantages:

(i) Cost increases with rise in the moisture content of solid waste. This is because energy is required for preheating the solid waste.

(ii) Ash formed after combustion has high concentrations of dangerous toxins such as dioxins and heavy metals. It results in air and water pollution.

19Solid Waste Disposal IncinerationThe controlled combustion of organic solid wastes so as to

convert them into incombustible residue and gaseous products. The weight and volume of solid waste is reduced and often energy is also produced.

Advantages: (i) As the volume of the waste is reduced so to take the

waste to the ultimate disposal site, less transportation cost is required.

(ii) Larger wastes can be accommodated in a given land fill area because incineration reduces the land requirement to one-third.

20Solid Waste Disposal Incineration Disadvantages:

(i) Not applicable for radioactive wastes. (ii) High capital and operational costs. (iii) Air pollution chances if incineration is not properly done. (iv) Highly trained man-power is needed.

Sources and Composition

Waste Properties

Solid waste System Storage, Collection and Transport

Recycling

Recycling

Recycling

Composition

Incineration

Landfill

Alternative Technologies

Solid Waste Management

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