Things that are thrown away because they are no longer of any use or requirement known as solid wastes.
Solid wastes include the domestic and industrial garbage’s such used newspapers and magazines, broken gases and glass conteners, plastic pieces, metalic scraps, aluminium material’s, wooden articles, polythene bags and so on. Solid wastes are major soil pollutants.
Soil is the superficial layer of earth crust which is essential like air and water. Soil is also essential directly and indirectly for the survival and maintenance of living organisms including man. Soil supports vegetation on which animals depend. Like air and water, soil may also get polluted.
Soil is polluted either directly by dumping and disposal of solid wastes or directly by air and water pollution. The major solid wastes that pollute soil are biocides used in agriculture, fertilizers, industrial solid wastes such as chemicals, flash and eniders which one residues of combustion of solid fuels, garbage, discarded food, paper, plastic, rubber, cloth, leather, asphalt, tin, building materials, dead animals, electrical and electronic home appliances including old computers. Huge quantity of solid wastes creates serious disposal problems.
All solid wastes can be categories into three types:
(b) Recyclable and
The kabadiwallahs and rag pickers do a great job of separation of materials for recycling. The biodegradable materials can be put into deep pits in the ground and may be left for degradation by micro-organisms in natural way. Now, the left out material is non-biodegradable which can be disposed off.
Care must be taken for safer land use, planned urbanization controlled developmental activities, safe disposal and the management of solid wastes. The last one involves collection, categorisation, transport to disposal site and disposal of the solid waste. Disposal of the waste consists of (1) Recovery and recycling, (2) Source reduction, (3) Burning and (4) Dumping.
Recovery and Recycling:
Some solid wastes like plastics, tincans, other metal scraps, glass, polyethylenes, rags, papers which are collected by rag pickers can be handed over to suitable plants for recycling. All these items after recycling are converted to new items. Not only this reduces soil pollution but also it is an economical way of best utilization of resources.
The need to reduce our garbage generation should be the primary goal. Solid waste generation at the point source should be restricted by created by public awareness.
Solid waste can be disposed of by burning. But, care should be taken not to create air pollution due to burning of solid waste. The following two processes are adopted to reduce solid waste by burning but not creating air pollution.
In this process, the garbages one burnt in very high temperature i.e. 900-1300°C in a furnace so that the volume reduces to 1/10. The ashes are collected and used as lawful material in building construction. They heat produced during incineration is also used for electricity generation.
It is destructive distillation under anaerobic condition. In this process, some of the solid wastes are subjected to combustion at temperature 1650°C, in the absence of oxygen. A wide variety of hydrocarbons with gases like CO2 or CO are formed as triproducts.
This technique is most useful in metropolitian cities where several tons of solid wastes are collected every day and there is only little space to dump them.
This is another way of solid waste disposal which can be done in the following ways:
(a) Open dumping:
In this process, solid wastes are dumped in large open areas which are far away from human habitation. They are regularly burnt and compressed at intervals to reduce volume and create space for further dumping.
(b) Sanitary landfill:
These are natural land scapes away of human habitation which are depressions or trench like areas. The wastes are dumped in them layer after layer, compressed and compacted and covered with earth. The surface so obtained by land fill can be used for sports field, animal grazing fields or even housing purpose.
(c) Ocean dumping:
In several developed countries like U.S.A., France, and England etc. Ocean dumping of domestic and industrial solid wastes is adopted. According to an estimate, by the year 1970 about 60 million tons of wastes were being disposed into ocean at over 200 disposing points in United States alone. However, this practice is gradually reducing due to their adverse effect over marine animals and navigation.