All nations in the world are engaged in improving their socio-economic conditions by utilising various natural resources. In this process, a large number of different kinds of industries and commercial activities have come up. As a result, urban areas and their population are increasing at a very fast rate.
From domestic and various commercial sources, a lot of solid waste is being generated and this is mostly responsible for environmental pollution and various health problems in the region and their surroundings. In view of this, it has become essential to properly manage urban solid waste, which is the single largest polluter, by applying the best available environment-friendly technologies.
The amount of solid waste generated all over the world is growing rapidly resulting in more complex problems due to the nature and amount of waste. For example, the amount of urban solid waste is growing fastest in China, which recently overtook the US as the world’s largest waste generator. It is reported that the amount of urban waste generated in the world will rise from the current 1.3 bn tonnes per year to 2.2 bn tonnes by 2025.
This waste, both solid and effluents results in a lot of pollution problems and causes a lot of health hazards to the urban population and also irreparable harm to the vegetation and animal life in the region. The annual cost of solid waste management in the world has been estimated to rise from 205 bn US dollars to 375 bn dollars with the cost increasing more sharply in less developed countries.
It is therefore essential that the best available environment-friendly and economical technologies be developed and properly applied in order to manage this waste satisfactorily. In less developed countries, the collection of solid waste and its processing is the single largest budget of the city authority. To keep the city healthy, the adoption of environment-friendly waste management practices is highly essential. It is reported that in near future with a fast-changing life system, “the challenges surrounding urban solid wastes are going to be enormous, on a scale if not greater than the challenges we are currently experiencing with climatic change”.
In recent decades, with rapid industrialisation and various commercial activities, there has been a mushroom growth of urban areas all over the world. In India, particularly after independence, the growth of urban areas and the shift of a large section of the rural population to these areas have been spectacular.
The urban population has been consuming various items in much larger quantities than their counterpart in rural areas. In the mad rush for having a high standard of living in urban areas and with the migration of a large number of the rural population in the search for employment, the urban areas have not only been crowded with slums but also are being polluted heavily due to release of huge quantities of various types of solid wastes, liquid effluents including the sewage and the pollution of the air with various poisonous gases like oxides of carbon, nitrogen and sulphur, especially from transport system and nearby industries.
In urban areas, out of all types of wastes and effluents, the amount and type of solid wastes generated are enormous and complex in nature. The municipal solid wastes include domestic waste, construction and demolition debris, hospital and sanitation residues, the garbage of street and commercial centres etc. With the increase in living standards and rising population in urban areas, these solid wastes are being piled up with very unsatisfactory disposal practices.
In 1947, the Indian cities and towns have generated about 6 million tonnes (MT) of solid waste, and these have increased to 48 MT within a period of 50 years. At present more than 25% of the total amount of municipal solid wastes is not collected and nearly 70% of the urban areas have unsatisfactory and inadequate capacity to transport and dispose of these wastes. Further, the existing landfill practices in most urban areas are unscientific and inadequate resulting in contamination of soil, water and air as well as the groundwater.
The primary steps involved in the management of waste are collection, sorting and separation, transfer and disposal. Necessary steps have to be taken to collect all types of solid wastes in urban areas in different localities and transport the materials to a centralized place where the organic matters, recyclable materials like plastic, glass, ceramic, metallic scraps and the building and roads debris can be separated out into mainly three fractions. Separating different types of waste material is very important. After separating out the wastes into three fractions, the recyclable materials should be sold to the respective industries, the organic fraction has to be processed for composting and fuel generation through aerobic or anaerobic digestion and the rest fraction should be used for landfilling as such or after incineration if the hazardous materials are present.
Technology Choices for Waste Management
Cost-Effective Collection Method
The urban solid waste collection system consumes a good portion of the expenditure for waste management as it is labour, fuel and vehicle intensive and also has to be repeated daily. In countries like India, the procedure for collection of waste as well as the cost are much more than those in developed countries. To make the collection method cost-effective one has to look into various alternatives like analysis of alternatives, the cost for labour, equipment, fuel, civil works, land etc.
To make the collection less costly, the urban residents should voluntarily collect their own wastes and deposit those in bin containers located by municipal authorities at their nearest sites. The door-to-door collection system by pushcart or any other similar carrier, would be more expensive. This system can be more effective if the people are ready to pay a little more.
Selection of proper collection system
A particular urban area should be divided into a number of sub-areas. In each sub-area, a number of smaller vehicles can be used for collecting the solid wastes deposited by individual houses from place to place and then these vehicles can transfer the wastes to a larger vehicle at a suitable site which would ultimately transport the wastes to the final disposal site.
Land disposal
The non-compostable wastes like building and road construction debris as well as ashes from incineration of wastes can be suitably used for landfilling using sanitary landfill techniques. This can be done after separating out the recyclable materials which are ultimately to be sold to the respective industries and the organic materials which can be utilised for composting.
Maximise efforts toward resource recovery
Most of the cost for solid waste disposal can be recovered by selling the recyclable materials (about 18% of the total wastes) to the respective industries and utilizing the organic wastes for composting as well as recovering the fuel value through anaerobic digestion in a centralized manner. The compost, as well as the fuel gas, can be sold to the respective customers.
Involvement of stakeholders related to waste management
The siting of land for the transfer station, landfill, incinerator, composting and biogas generator etc. is very important for urban waste disposal and it is generally opposed by the people living in nearby areas. In this case, the cooperation of the affected people should be obtained to undertake the urban waste management programmes by giving jobs and providing other incentives to them. It would be preferable to select the waste disposal sites which are away from the residential and farming lands as well as water bodies, roads etc.
In urban India, particularly in densely populated areas, the burning of wastes containing plastic bags and other materials are highly health hazard due to the production of very toxic fumes such as furans and dioxins. Burning of organic wastes, in general, is highly harmful to the environment as this is the major source of greenhouse gases contributing immensely to global climate change and hazardous to the health of people.
The best system to manage the urban solid wastes should be to streamline the collection, transportation and treatment of the wastes by adopting modern technology. At first, the recyclable wastes like metal scraps, plastics, rubber, glasses etc. should be separated and sold to the respective industries. Then, the organic waste should be separated out for utilising in anaerobic digestion for producing fuel gas as well as compost and the rest residue has to be utilized for landfilling in a scientific manner.
The waste processing facility for every urban area should be away from habitation, roads and water bodies. If urban waste management is carried out scientifically as mentioned above, most of the cost can be realised by selling the recyclable materials to the respective industries, compost to the farmers and fuel gas to the urban dwellers for power generation or domestic fuel purposes. These programmes can be successful with full cooperation between the public and the local government and in this regard, the former should be educated about the benefits they can derive from this.
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