Wastes are chemical by-products of an industry, a factory or a chemical plant. They may result from household activity/a hospital or a research laboratory.
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Solid waste is the solid chemical produced by any of these sources, which may be dangerous to human health and pollute the environment. Waste may be classified into two categories:
Toxic waste (intrinsic characteristic)
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Toxicity is the capacity of a substance to produce injury after entering the metabolic processes of the consumers (an animal, a plant or a human being). The changes may be pathogenic/mutagenic/tetragonic or carcinogenic.
Hazardous waste (extrinsic characteristic)
Hazardous means the potential of a substance to pose threat to life. Hazardous wastes have the properties like toxicity, ignitibility, corrosiveness, reactivity, radioactivity or explosiveness. Hence, the term hazardous is brooder that includes “toxic” word in its spectrum.
Solid waste management
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Waste management has become an important environmental and public health issue, which concerns many countries in the world; waste management can be done by the following four methods:
i) Waste minimization (by minimization the quantity of waste)
Three major waste minimization techniques are:
a) Process modification
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Industrial processes can be altered in such a way that the use of raw materials is optimized and the amount of waste is reduced.
b) Waste concentration
The large amount of waste can be minimized by concentration processes like evaporation, precipitation or decantation technique. Volume of waste can be minimized by this technique.
c) Waste segregation
Segregating the waste streams from non-hazardous streams can minimize the volume of waste.
ii) Treatment of waste
The aim of treatment of waste is to modify the physical and /or chemical properties of the wastes so that they are rendered harmless. Selection of treatment process depends upon nature of waste, economic and energy consideration,
a) Biological treatment
Solid waste minimization is done by biological treatment of the waste before disposal. This treatment include three processes
Conditioning
In this process, the solid is exposed to atmosphere for a stipulated period until the desired constancy is reached.
Digestion
Waste is treated with bacteria in this process. The bacteria break down the long chain compounds into simpler ones.
Composting
In this process the waste is converted into the usable stable material.
iii) Recycling of wastes
Many substances in the solid wastes (glass, wood fibre from the paper products and metals) are variable and can be utilized after recycling the waste. The two processes are often used to recycle the waste.
1. Reuse of the waste
2. Recycling of the waste
iv) Disposal of waste material
There are four different ways of disposal of solid waste material:
1. Landfill disposal
2. Incineration (burning of waste products)
3. dumping at sea (for prevention of ground water pollution, disposal of waste is controlled by international legislation and by national legislation).
4. Underground disposal (underground disposal may provide an environmentally and economically viable option for radioactive wastes).