Solid Waste Management

• Refuse sanitation or Solid Waste Management is the process of collection, transportation and disposal of solid waste in a systematic, economic and hygienic manner.
• CLASSIFICATION OF SOLIDS WASTES BASED ON THEIR SOURCES OF ORIGIN?

  Residential Wastes

  Commercial Wastes

  Institutional Wastes

  Municipal Wastes

  Industrial Wastes

  Agricultural Wastes
• Residential wastes: generated from domestic operations in a house as vegetable peels, leftover food, pieces of wornout plastics, rags of clothes, waste papers, ashes etc.
• Commercial wastes: from business establishments as pieces of glasses, metals, ashes and food wastes from restaurants, markets, hotels etc.
• Institutional wastes: from schools, colleges, hostels, offices which comprise paper, plastics, glasses etc.
• Municipal wastes: arising from street cleaning and maintenance of parks. They include dust, leafy matter, building debris, treatment plant residual sludge and building demolition and construction wastes.
• Industrial wastes: arising due to industrial activities. They vary widely from industry to industry. They range from inert wastes to hazardous end products.
• Agricultural wastes as agricultural remains, spoiled food grains and vegetable peelings.
• CLASSIFICATION BASED ON PHYSICAL NATURE?

  Garbage

  Ashes and Residues

  Combustible and Non-Combustible Wastes

  Demolition and Construction Wastes

  Hazardous Wastes
• Garbage: It is semi solid waste resulting from handling, sale, storage, preparation, cooking and consumption of food of vegetable and animal origin. They contain putrescible organic matter giving out obnoxious odour with time.
• Ashes and residues: These are residues of combustion resulting from the burning of wood, coal, coke and other combustible materials. They are black fine powdery and dusty inert solids rich in carbon content.
• Combustible and non-combustible wastes: They are inert wastes of households, community and commercial activities. Pieces of paper, cardboard, plastics, leather, textile and rubber which are combustible and give out very less ash are of one type. Non-combustible wastes of materials as tin and aluminum cans, ferrous and non-ferrous material, broken glass, house sweepings as sand are the other type.
• Demolition and construction wastes: Demolition of existing structures give out bulky wastes of varied nature as earth, stones, concrete, bricks, ceramics, roofing and plumbing materials, heating systems and electrical wires etc. and a mixture thereof. Wastes are also generated during construction of buildings but they are less in quantity and of uniform nature, as dust of bricks, cement etc.
• Hazardous wastes: Hazardous wastes are toxic, corrosive, reactive or ignitable and hence are to be carefully preserved and separately disposed of.
• Properties of Solid Waste?

  Particle Size

  Moisture Content

  Density
• Particle size is the size of the biggest particle in a lump. Smaller the particle, difficult is its collection, conveyance, handling and segregation. However smaller organic matter has greater surface area and hence decomposes quickly.
• Moisture content: It is the percentage of moisture retained by the solid waste of unit weight. Moisture content of solid varies very widely i.e. from 10% to 90% depending on the nature of waste, precipitation, environment and climatic zone.
• Greater moisture content increases the weight of solid waste and hence cost of collection and transportation. Segregation of waste slows down because of greater moisture content. Cost of incineration increases with moisture content.
• Density is the weight in ‘kg’ of ‘cubic metre ‘ of solid waste in normal (i.e. loose and not compacted) state. Greater the density less is the volume occupied and easier is the collection, transportation and handling. Density of solid waste in a landfill after repeated compactions may rarely exceed 600 kg/m3.
• Chemical Properties?

  Inert

  Degradable
• Inert: as building demolition wastes whose volume remain the same irrespective of time. No gases of decomposition emanate out of them.
• Degradable: undergoing decomposition or degradation physically, chemically or biologically. Their volume reduces with time. Gases of decomposition are given out.
• Carbohydrates: They are mostly found in solid wastes from underdeveloped and developing countries. They are starches and cellulose of composition and principally contain carbon, oxygen and hydrogen. They readily decompose to give out carbondioxide and water and also methane under anaerobic conditions. Flies and rodents are easily attracted towards decomposing carbohydrates and hence they should be properly protected.
• Proteins: (COHN)X is their general composition i.e. they have nitrogen in addition to carbohydrates. They constitute major portion of wastes from affluent countries but relatively less in poorer countries. They decompose slowly compared to carbohydrates and offensive odours as ammonia are given out in addition to CO2, CH4 and water vapour.
• Lipids: Lipids are fats, oils and greases and mainly contain carbon, oxygen and hydrogen. They are slow to degrade. They have very high heating values of around 38,000 kJ/kg.
• Fibres: of vegetable origin as those from coconut shells, bamboo, sugar cane etc., are of cellulose and lignin. Papers and rags are the common sources of fibres. They are very resistant to biological degradation but are readily combustible. yielding 12,000 to 20,000 kJ per kg.
• Plastics: are synthetic organic materials, highly resistant to biodegradation and hence are highly objectionable. They constitute 1 to 10% of the total volume of solid wastes and this percentage is rising from year to year.
• Factors influencing solid waste management?

  Per capita income and status

  Climate and percentage moisture

  Systematic growth of city

  Status of the municipality

  Customs and practices

  Resources available
• Per capita income and status: Higher the income more is the quantity of solid waste produced. 0.25 to 2.5 kg/capita/day is roughly the quantity of municipal solid waste produced in India. More is the quantity of waste greater is the content of paper and packing materials.
• Climate and percentage moisture: While the percentage of moisture is less than 50% in summer months, it is more than 65% in wet weather. It is easy to collect and transport solid wastes in dry climate and collection and handling are difficult in wet weather. Quantity of leachate is less during dry weather and is more during wet weather. Decomposition is accelerated with increase in moisture and temperature. Hence clearing interval (of solid wastes) is smaller in hot and humid climate while it can be longer in cold and dry climate.
• Systematic growth of city: A planned town of wide roads and stream lined growth of houses facilitates easy collection of refuse and hence bigger or smaller containers at regular intervals for refuse collection may be provided. An irregularly grown old town or outskirts of a town with ribbon development pose problems of collection. Hence smaller containers at closer intervals need be provided as the lanes are narrow and of irregular alignment.
• Status of the municipality: The income, expenditure and funds to be allotted for street cleaning and disposal of solid wastes do influence the method. A rich municipality can afford more spending on solid waste management. It can maintain a crew of permanent employees and fleet of vehicles involved in collection, transportation and disposal of the solid waste (i.e. for compaction). It can own disposal sites. A poor municipality has to hire the crew and trucks for transportation on a temporary basis. It has to take disposal sites on temporary lien.
• Customs and practices: Customs differ from community to community and from street to street of a town. A posh locality may contribute more solid waste but almost of the same nature. Middle income group residences may contribute solid wastes of quite diversified natures.
• Resources available: Based on the technical skills of skilled persons available, unskilled men and women labour available, the extent of site available for disposal of wastes, one should arrive at optimum utilization of their services to get the best desirable outcome.
• To asses the management possibilities it is important to consider?

  (i) origin of solid wastes

  (ii) reduction of raw materials usage

  (iii) reduction in amount of solid waste

  (iv) reuse of waste materials

  (v) salvaging
• Origin of solid wastes: Solid wastes are generated at different stages as (a) extraction of raw materials i.e. mining as in metallurgical processes or crop extraction as sugar cane cutting in sugar industry or bamboo cutting in paper production. (b) every stage of operation – converting raw materials into the finished product.
• Reducing quantity of raw materials: It can be achieved by better techniques as (a) condemning the old machinery whose efficiency is low (b) improving the output by adopting better technology.
• Reduction in quantities of solid wastes: It can be done by reusing or recycling some of the wastes generated so that the quantity of waste generated is considerably reduced per tonne of the product produced.
• Segregation and recovery: Segregate the solid waste to extract valuable products as metals. Even inferior wastes as “Baggasse” in a sugar mill can be utulized as a fuel to generate steam in industrial operation or for the preparation of pulp in paper making. Fibres of coconut can be used in coir industry.
• Salvaging: Food content of organic matter can be effectively used as hog feed or poultry feed. Similarly good manure can be extracted from domestic solid wastes.