Essay on Solid Wastes: Sources, Effects and Management

After reading this essay you will learn about:- 1. Sources of Solid Wastes 2. Effects of Solid Wastes 3. Management 4. Discarding of Solid Wastes.

Sources of Solid Wastes:

Urban waste consists of medical waste from hospitals; municipal solid wastes from homes, offices, markets (commercial waste) small cottage units, and horticulture waste from parks, gardens, orchards etc.

i. Domestic Waste:

Contains a variety of discarded materials like polyethylene bags, empty metal and aluminium cans, scrap metals, glass bottles, waste paper, diapers, cloth/rags, food waste etc.

ii. Waste from Shops:

Waste from shops mainly consists of waste paper, packaging materials, cans, bottles, polyethylene bags, peanut snails, eggshells, tea leaves etc.

iii. Biomedical Wastes:

Biomedical wastes include anatomical wastes, pathological wastes, infectious wastes etc.

iv. Construction/Demolition Waste:

Construction/demolition waste includes debris and rubbles, wood, concrete etc.

v. Agri-Horticultural Wastes:

Slaughter houses include vegetable parts, residues and remains of slaughtered animals, respectively. The urban solid waste materials that can be degraded by micro-organisms are called biodegradable wastes. Examples of this type of waste are vegetable wastes, stale food, tea leaves, egg shells, peanut shells, dry leaves etc. Wastes that cannot be degraded by micro-organisms are called non-biodegradable wastes. For example, polyethylene bags, scrap metal, glass bottles etc.

vi. Industrial waste:

Industrial waste consists of a large number of materials including factory rubbish, packaging material, organic wastes, acids alkalis and metals etc. During some industrial processing large quantities of hazardous and toxic materials are also produced. The main sources of industrial wastes are chemical industries, metal and mineral processing industries.

Radioactive wastes are generated by nuclear power plants. Thermal power plants produce fly ash in large quantities. Solid wastes from other types of industries include scrap metal, rubber, plastic, paper, glass, wood, oils, paints, asphalt, tars, dyes, scrap leather, ceramics, abrasives, slag, heavy metals, asbestos, and batteries.

Effects of Solid Wastes:

Municipal solid wastes heap up on the roads due to improper disposal system. People clean their own houses and litter their immediate surroundings which affect the community including themselves. This type of dumping allows biodegradable materials to decompose under uncontrolled and unhygienic conditions. This produces foul smell and breeds various types of insects and infectious organisms besides spoiling the aesthetics of the site.

Industrial solid wastes are sources of toxic metals and hazardous wastes, which may spread on land and can cause changes in physicochemical and biological characteristics thereby affecting productivity of soils. Toxic substances may leach or percolate to contaminate the ground water.

In refuse mixing the hazardous wastes are mixed with garbage and other combustible waste. This makes segregation and disposal all the more difficult and risky. Various types of wastes like cans, pesticides, cleaning solvents, batteries (zinc, lead or mercury) radioactive materials, plastics are mixed up with paper, scraps and other non-toxic materials which could be recycled. Burning of some of these materials produce dioxins, furans and polychlorinated biphenyls, which have the potential to cause various types of ailments including cancer.

Management of Solid Waste:

For waste management we stress on ‘three R’s’—Reduce, reuse and recycle before destruction and safe storage of wastes.

(i) Reduction in use of Raw Materials:

Reduction in the use of raw materials will correspondingly decrease the production of waste. Reduced demand for any metallic product will decrease the mining of their metal and cause less production of waste.

(ii) Reuse of Waste Materials:

The refillable containers which are discarded after use can be reused. Villagers make casseroles and silos from waste paper and other waste materials. Making rubber rings from the discarded cycle tubes which are used by the newspaper vendors, instead of rubber bands, reduces the waste generation during manufacturing of rubber bands. Because of financial constraints poor people re-use their materials to the maximum.

(iii) Recycling of Materials:

Recycling is the reprocessing of discarded materials into new useful products.

(i) Formation of some old type products e.g. aluminium cans and glass bottles are melted and recast into new cans and bottles.

(ii)Formation of new products. Preparation of cellulose insulation from paper, preparation of fuel pellets from kitchen waste. Preparation of automobiles and construction materials from steel cans.

The process of reducing, reusing and recycling saves money, energy, raw materials, land space and also reduces pollution. Recycling of paper will reduce cutting of trees for making fresh paper. Reuse of metals will reduce mining and melting of ores for recovery of metals from ores and prevent pollution.

Discarding of Solid Waste:

For discarding wastes the following methods can be adopted:

(i) Sanitary Landfill:

In a sanitary landfill, garbage is spread out in thin layers, compacted and covered with clay or plastic foam. In the modern landfills the bottom is covered with an impermeable liner, usually several layers of clay, thick plastic and sand. The liner protects the ground water from being contaminated due to percolation of leachate.

Leachate from bottom is pumped and sent for treatment. When landfill is full it is covered with clay, sand, gravel and top soil to prevent seepage of water. Several wells are drilled near the landfill site to monitor if any leakage is contaminating ground water. Methane produced by anaerobic decomposition is collected and burnt to produce electricity or heat.

(ii) Composting:

Due to shortage of space for landfill in bigger cities, the biodegradable yard waste (kept separate from the municipal waste) is allowed to degrade or decompose in an oxygen rich medium. A good quality nutrient rich and environmental friendly manure is formed which improves the soil conditions and fertility.

(iii) Incineration:

Incinerators are burning plants capable of burning a large amount of materials at high temperature. The initial cost is very high. During incineration high levels of dioxins, furans, lead and cadmium may be emitted with the fly ash of incinerator.

Dioxin level may reach many times more than in the ambient environment. For incineration of materials, it is better to remove batteries containing heavy metals and plastic containing chlorine before burning the materials. Prior removal of plastics will reduce emissions of dioxins and polychlorinated biphenyls (PCBs).