Solid Waste

Anything that is not of further use in a process is known as waste for that process. That can be useful for other process and can be termed as raw material for that process. So actually waste is a misplaced resource. When this waste is in a comparatively solid form it is known as the solid waste. Whatever may be the form of waste, it deteriorates the environment  if  it  is  disposed  in  an  offensive  manner.  The  waste  water  and  its treatment and disposal have already been discussed.

Solid waste is defined as discarded solid fraction produced from domestic, commercial, trade, industrial, agricultural, institutional, mining activities and public services. The waste is a term that means useless, unwanted or discarded material.

According to the American Public Works Association the solid waste is classified in twelve categories as, garbage, rubbish, ashes, Street sweepings, dead animals, abandoned  vehicles,  construction/demolition  waste,  industrial  refuse,  special  waste such as hospital waste, bulky waste, animal and agricultural waste, and sewage treatment residue (semi solid fraction known as sludge).

Solid waste includes domestic waste, municipal waste, commercial waste, garbage (animal and vegetable waste), rubbish (inorganic excluding ashes), ashes and industrial waste, sludge from wastewater treatment plants etc. Actually, mainly the population living in the urban area produces much more solid waste than the rural one. As there is more employment potential in urban area the urban population has increased from10.84% in 1901 to 25.7% in 1991. The class I cities has increased from 212 to 300 during 1981 to 1991, while class II cities has increased from 270 to 345 in the same period.

As the living style in urban area is totally different from rural area (sanitary system, industrialization etc.), much more solid waste is produced in urban area. Actually more is the (so called) advancement, higher is the solid waste production. Because of poverty, life style, the habit of living with nature and lesser population density, lesser waste is produced in rural areas of our country. So basically solid waste problem is more related to the cities or towns and as the cities are increasing the problem is being aggravated.

To handle the problem of solid waste in an efficient manner is known as the solid waste management. This management is a part of public health and sanitation and as per the Indian constitution it is the responsibility of states. In the states various local bodies like municipalities (in towns) or the municipal corporations (in cities) or the development authorities (in big cities) are to deal with solid waste management. Generally, the water supply and electricity are on the top priority of the state government and because of various reasons even they are in short supply. Then comes the collection conveyance treatment and disposal of wastewater. Unfortunately, the solid waste management comes on the last priority.

Only a few efforts have been made to create community awareness about the bad effects of poor solid waste management or to reduce the generation of solid waste. Because of the poor education system and lack of strong will power there is no successful systems of solid waste management in any city of India (with a very few exceptions). There is practically no penalty for throwing anything on the roads or the nearby premises. Nobody, minds and cares in living in such foul conditions. When it end in a calamity like the recent plague in Surat city of Gujarat, only then we think about the solid waste management, and that too only for some days. The basic thinking process of the society has rotten. Nobody, minds in misusing every resource if it is money wise affordable. Actually, waste is a misplaced resource.

If we plan in such a way that there is a thoughtful consumption of every thing, nothing shall come out as ‘waste’. Nature has given us many cycles by which everything  becomes  useful  and  regenerated.  The  organic  matter  (nightsoil,  excreta, food, vegetable, paper) can be converted into useful biogas and compost. Everybody knows about it. But the problem is of separating it from the inorganic waste like ashes, rubbish, non bio-degradable waste. When the solid waste is a mixture of all these, the separation or segregation becomes costly.

The segregation is a must otherwise the extraction of energy in the form of gas, heat or fertilizer is not possible or uneconomical. So, this segregation must be done at the producer end. The producer must either have some incentive or penalty for this. Unfortunately both are not there in our country and the required wisdom is also not there.

So we are living on a heap of solid waste in most of the places. It is estimated that the total solid waste generated by 300 million people in urban India is 38 million tons per year. Or in other words it is estimated that 1,00,000 ton of municipal solid waste is generated in India daily. Depending upon the status of the city the per capita generation of solid waste is from 0.2 to 0.6 kg per day. Higher is the status more amount of the waste is produced.   In so called advanced countries this figure is much more, but there they observe strict rules and regulations. Even the dogs are not allowed to defecate on the roads where as in India it is a common practice for the human beings living in slums without a toilet.

The problem other than generation of solid waste is its misplacement. Most of the solid waste generated inside the premises are thrown on the roads. There is no effective door to door collection system or a self motivated culture of putting the waste in the bins or at the designated places for it. Consequently the 60 to 70% of the megre budget available with the municipalities is spent in street sweepings. 20 to 30% of the budget is spent in transporting it to the disposal site. Thus, hardly 5% remains for scientific sanitary disposal of the waste and so it is either burnt in open to produce harmful gases or left to scatter here and there. If it is dumped as such it pollutes the soil, rain water or the ground water by leachates (dark concentrated foul wastewater produced by the decomposition of biodegradable matter in absence of oxygen).

So there is an urgent need of understanding the mechanism of solid waste management. For this purpose first of all let us discuss the classification of solid waste.

CLASSIFICATION OF SOLID WASTE

The  solid  waste  can  be  classified  as  per  the  Manual  on  Municipal  Solid  Waste

Management, Government of India publication as follows:

• Domestic/Residential  waste: This type of waste is originated from single or multifamily household units. These wastes are generated from the household activities such as cooking (ashes) cleaning (dust) repairs (residues), hobbies (unuseables), redecoration, empty containers, used packets, old clothes, books, papers, broken glass, plastic items, broken and useless furniture.

• Municipal  waste: Municipal waste includes waste resulting from municipal activities and services such as street sweepings, dead animals, market waste and abandoned vehicles. Generally, this term ‘Municipal Waste’ is used in a wider sense to incorporate domestic wastes, institutional wastes and commercial wastes.

• Commercial  waste: This  category  includes  solid  wastes  that  originate  in offices, wholesale and retail markets, restaurants, hotels, warehouses (godowns) and  other  commercial  establishments.

• Institutional waste: These are those wastes generated from institutions such as schools, colleges, universities, hospitals and research institutes. Some of these wastes (like hospitals) may be hazardous (more bad, offensive, strong, disease  producing)  waste.

• Garbage: Garbage is the term applied to animal and vegetable wastes gen- erated from the handling, storage, sale, preparation, cooking and serving of food. Such wastes contain putrescible (easily and quickly biodegraded with bad smell) organic matter. This attracts rats, flies, mosquito and other vermin, that is why it requires immediate attention.

• Rubbish: It is a general term applied to solid wastes originating in households, commercial establishments and institutions excluding garbage and ashes.
• Ashes: These are the residues from the burning of wood, coal, charcoal, coke and other combustible matter for cooking and heating in houses institutions and small industries. When produced in large quantities in thermal power plants (fly ash) they are known as industrial wastes. Ashes consists of fine powdery residue, cinders and clinkers often mixed with small pieces of metal and glass.
• Bulky  waste: Bulky  wastes  are  large  household  wastes  that  cannot  be accomodated in the normal storage containers of the household and thus they require special collection. Actually in India there is hardly any waste collected in this category as it is sold to the kabaries.
• Street sweepings: The waste collected from streets, walkways, parks etc. is known as street sweepings. In developing countries like our country manual street sweeping is done and it makes the largest portion of the municipal solid waste as we are in a habit of throwing everything on the streets. It includes mainly dust, dirt, plastic bags (thin), dry leaves, useless papers, cardboard, rags, tyres, vegetable matter etc. In our country most of the usable portion of the waste like rags, paper, thick plastic bags, plastic utensils, any form of metal is collected by the rag pickers. The organic matter including the paper and even plastic sheets is consumed by cows and other stray animals. Only in big cities or the developed countries they form the part of waste. That is why the calorific value of Indian solid waste is far less in comparison to the other  countries.
• Dead animals: This term includes the dead animals that die naturally or by accidents on roads. It does not include the animal parts from slaughter houses which are regarded as industrial waste. There are two types of dead animals, large and small. The smaller ones like dogs cats rabbits, rats etc., are either consumed by the other animals or can be easily lifted and disposed. The large ones like cows, horses, camels etc. require special and immediate attention as traffic is affected and they emit foul smell.
• Construction and demolition waste: These are the wastes generated by the residue of the construction, refurnishment, repair and demolition of houses, commercial buildings and other structures. Generally, the demolition waste is used by the contractors in filling low lying areas and the plinth filling of new houses and nothing is left on the sites. Even then some small quantity of sand, stone or concrete may be left.
• Industrial wastes: The discarded solid material of manufacturing processes and  industrial  operations  comes  in  this  category.  There  is  a  vast  range  of substances that are unique for each industry so they are considered separately from  municipal  wastes.
• Hazardous  waste: Hazardous  waste  is  defined  as  wastes  of  industrial, instutional or consumer origin that, because of their physical, chemical or biological characteristics are potentially dangerous to human beings and the environment. In some cases the active agents may be liquid or gaseous, they are classified as solid waste because they are confined in solid containers. Typical examples are solvents, paints, and pesticides whose spent (empty) containers are frequently mixed with municipal wastes and become part of the urban waste stream. Certain hazardous waste can explode in the incin- erators (controlled large kilns) and cause fires at land fill sites. Others such as pathological (disease producing) wastes from hospitals and radioactive waste, require special handling at all times. Proper management practice should ensure that hazardous wastes are collected, stored, transported and disposed off seprately, preferably after treatment to make them harmless.
• Sewage  waste: The solid by-products of sewage treatment are classified as sewage wastes. They are mostly organic and produced from the treatment of organic sludge from both the raw and treated sewage. The inorganic fraction of raw sewage such as grit is separated at the preliminary stage of treatment, but because it entrains putrescible organic matter that may contain disease producing bacteria (pathogens), must be buried or disposed off quickly.

Importance of Classification

Any one method of classification of solid waste is not sufficient because of the heterogeneous nature of solid wastes. Actually, the real knowledge of solid waste characteristics is very much essential to conceive the treatment and disposal. Sometimes the waste is disposed with extraction of energy out of it. For example electricity is generated or biogas is produced. In both these cases the waste must have a minimum value of calorific value or the organic matter respectively.

It has happened in many cases like that of plant in Timarpur that did not work due to the different characteristics of the waste than those for which the plant was designed. Actually, the plant are generally imported and are based on higher calorific value solid waste whereas the average Indian solid waste has larger fraction of inorganic waste (dust, dirt, silt etc.), with lesser organic matter (vegetable, paper and other combustible matter), and hence has a very low calorific value (Kcal/Kg).  So the knowledge of the characteristics and composition of the solid waste is utmost important.

COMPOSITION AND CHARACTERISTICS OF SOLID WASTE

The composition and characteristics of municipal solid waste is not same throughout the world and even in the same country it changes from place to place and time to time. As explained earlier it depends upon the living standard, social customs, location of a place, climate and weather conditions etc. Higher is the standard of living, more is the waste produced. Alongwith the total quantity of waste produced, the composition of waste is also different for different income groups.

Characteristics of Municipal Solid Waste in Indian Cities

As explained earlier the character of municipal solid waste is variable because of many reasons. It depends mainly upon the monetary level, but also the size of the city, its geographical conditions and the lifestyle. Simple conclusions cannot be drawn in each case and thus the solution to the problem of solid waste management should be site specific. The following table shows the research data from National Environmental Engineering Research Institute (NEERI), Nagpur. It is evident from the table that every result is not but obvious and there are so many things that are to be explored before reaching  to  a  conclusion.

EXPECTED QUANTITIES OF SOLID WASTE

For the assessment of collection, conveyance, treatment and disposal, the expected quantities of solid waste generated in a locality must be known. NEERI has done extensive work and has measured the quantities of waste generated in the Indian cities. The quantity of waste produced is lesser in Indian cities as compared to the developed countries, because of the poverty and the way of living. Ours is a more natural way of living and nature has its cycles to recycle the waste. In India the average solid waste produced per capita per day vary between 0.2-0.6 kg/capita/day, the higher value is for metropolitan cities. The total solid waste generated in urban area (towns with population more than 5000 and having other amenities) is estimated to be around 38 million tones per annum.

The actual forecast of waste quantity is as difficult as is estimation of the waste composition. The quantity also depends upon the living standard, size of the community, climate, particular days ( like Diwali and other festivals), etc. Alongwith the quantity the density of the waste is also variable and it changes with the storage method, salvaging (sorting) activities, exposure to weather, handling methods and decomposition. It can be noted as a general rule that the lower is the level of economic development, the greater is the change in the density of waste from generation and disposal. The waste in developing countries get compacted upto the disposal point in such a way that its volume reduces to half.

WASTE MANAGEMENT APPROACH

The solid waste management has a two fold approach. First is the minimization of waste at the source and other is the control on environmental pollution during its storage, conveyance  and  disposal.

Prevention is always better than cure. If the production of waste can be reduced at the source level it shall reduce the cost of conveyance treatment, disposal and  shall save the environment. The waste minimization techniques are grouped in four major categories for hazardous as well as non hazardous waste, as follows:

Inventory Management and Improved Operation

•    Inventorisation (making stock registers) and tracing of all raw materials.

•    Purchasing of lesser toxic and more non-toxic production material.

•    Implementation  of  employee’s  training  and  management  feedback.

•    Improving  material  receiving,  storage  and  handling  practices.

Modification of equipment

•    Installation of equipment that produce minimum waste.

•    Modification of equipment to enhance recovery or recycling options.

•    Redesigning of equipment or production lines to produce less waste.

•    Improving operating efficiency of equipment.

•    Observing  strict  preventive  maintenance  programme.

Modifications in Production Process

•    Selection  of  non-hazardous  raw  material.

•    Segregation of waste for recovery.

•    Identification  and  elimination  of  leakages.

•    Optimization  of  reactions  and  raw  material  use.

Recycling and reuse

•    Installation of closed-loop systems

•    Recycling off site for another use

•    Exchange  of  wastes

By adopting the above waste minimization techniques the waste is minimized at the source so that its handling and transportation charges are reduced and lesser efforts are to be done in disposal.