The wastes which are produced as a result of human, agricultural, industrial and biomedical activities need to be collected from the sources where they are produced, transported and disposed of in the right way so that they do not cause harm to the environment and human beings.
The programme of waste management should evaluate local needs and conditions and accordingly select a combination of the most suitable methods of waste management and disposal. There are three major steps involved in the proper management of solid waste, which also include the municipal solid waste (MSW). They are:
1. Collection and Segregation
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2. Transportation
3. Disposal.
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1. Collection and Segregation of Waste:
The first step in the management of waste is the collection of waste. The accumulated waste heaps should be sorted out in different types before transportation. We should collect the similar types of waste in different waste bins.
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The municipal waste has biodegradable and no biodegradable wastes. The non-biodegradable wastes include plastics, used metal cans and other items, broken glass and china clay pieces, etc.
The wastes should be segregated at source as different types of waste need to be disposed of in different manner. It is more profitable and economical to segregate the waste at the source.
In residential areas, the waste can be separated by using different coloured bins in which the residents can throw the waste accordingly. For example, blue coloured bins can be used for non-biodegradable waste and green coloured for biodegradable waste.
The biomedical waste should be segregated and packed in different leak proof, colour coded plastic bags or bins to facilitate identification, storage, transportation and safe disposal of these hazardous wastes.
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The segregation of waste into different categories is an essential step in the disposal of solid waste, as each category of waste is disposed of differently according to their nature and level of toxicity.
2. Transportation of Waste:
From the places where the waste has accumulated or collected, the local agencies engaged in the management of the municipal waste, should carry away the collected waste in trolleys or vans to the place of disposal.
The vehicles, which are used for transporting the waste, should be covered to prevent the waste from scattering. The waste as far as possible shall not be visible to the public or exposed to the open environment.
The liquid waste from the kitchen and toilets should be transported to the disposal and treatment plants through the sewer lines.
To reduce the risk of exposure of biomedical waste to the public and to the environment, rigid containers should be used for transporting the colour coded bags to the disposal site.
3. Methods of Waste Disposal:
The common methods used for disposal of solid waste in different parts of the world are open dumping, landfill, composting, drainage, incineration, recycling and reuse. In most of the developing or underdeveloped countries, the most popular methods are dumping and landfill.
In most of the underdeveloped and developing countries, the waste materials are dumped in open grounds, away from the city or town, and left to decompose. This conventional, inexpensive and widely used method of waste disposal has several disadvantages. It is harmful for the environment as well as for humans and other living organisms.
The solid waste materials which are left in the open give out bad odour and are the breeding grounds for mosquitoes, flies and other harmful bacteria. This can cause a variety of diseases. Sometimes the rain can wash away this waste to nearby waterbodies like rivers, streams, lakes or pond.
These waterbodies get polluted. If these wastes are absorbed in the soil, they can easily pollute-the groundwater. This method of dumping the waste in open areas is being replaced by the landfilling of waste.
It is now a widely used method for municipal solid waste disposal. In this method, the landfills are covered with earth, so that insects do not enter these landfills. The wastes are then left to decompose. A number of physical, chemical and biological reactions take place and a variety of toxic gases, such as carbon dioxide, methane, ammonia and hydrogen sulphide, are released.
The landfills are generally far away from residential areas. This method has the following advantages:
1. There is no pollution of air, as the landfills are covered by earth.
2. The health hazards are few, as the mosquitoes and rats do not breed.
3. It is most suitable for non-biodegradable waste, which is not suitable for composting, recycle or reuse.
4. It is free from fire hazards.
Composting is a natural biodegradation process in which the biodegradable solid wastes can be converted into nutrient-rich manure in the presence of microorganisms. Composting can be done either in the presence of atmospheric air (aerobic composting) or in the absence of atmospheric air (anaerobic composting).
The aerobic composting is more common in our country, due to the ease with which it can be practised. However, it is less economical and leads to emission of greenhouse gases. This method is more prevalent in agriculture based areas, as this method requires the decaying plants, leaves, etc. to be buried in a small pit and left to decay. It has the following advantages:
1. It enhances the soil nutrients, such as nitrogen and phosphorus.
2. It enhances the water retention capacity of the soil.
3. It increases the fertility of soil by adding humus.
4. It works as a natural waste disposal system.
Vermicomposting is another method, in which manure is obtained from biodegradable waste by adding earthworms to the compost. The earthworms help in degrading the waste and the excreta of the worms makes the compost rich in nutrients.
Drainage is a system in which water is removed from the surface or subsurface area (residential, agricultural or industrial) by artificial or natural methods. In this system channels are constructed to allow the water flow from surface or subsurface. If the channels are properly built in a planned manner, it can prevent soil erosion. It also helps in preventing excessive accumulation of soluble salts in the soil, which may be harmful to the growth of plants.