Rapid economic growth is leading to urbanization and industrialization, generating waste which is adversely affecting the environment.
“Wastes” are materials which are discarded after use at the end of their intended lifespan. Waste management is a collective activity involving segregation, collection, transportation, re-processing, recycling and disposal of various types of wastes.
Types of Waste:
Waste matter can broadly be divided as:
1. Solid Wastes:
It includes left-over food, decaying fruits and vegetables, crop residues, cans, bottles, metal pieces, plastics, wrappers, ashes, body parts of dead animals, etc.
2. Liquid Wastes:
It includes sewage from toilets of houses, hospitals, restaurants, offices and factories, oil spills etc.
3. Gaseous Wastes:
It includes fuel exhausts containing carbon dioxide, nitrogen oxides, carbon monoxide, sulphur dioxide and smog etc.
i. Toxic Waste:
Toxic wastes are the wastes that pose a serious threat to human health and environment. These wastes result from industrial processes, chemical fertilisers in agriculture, biomedical waste generated in the hospitals, radioactive wastes, electronic waste or e-waste generated from computers, mobile phones and electronics.
Some of the toxic wastes are arsenic, cyanide, lead, cadmium, nickel, beryllium, uranium, mercury and their compounds, chlorinated solvents, asbestos, organo-chlorine pesticides, photographic wastes, plating sludges, pesticide residues, waste paints and lubricants. Burning produces oxides of sulphur and nitrogen which become toxic at high concentration.
ii. Non-Toxic Waste:
Some of the solid wastes such as food leftovers, fruit and vegetable peels generated due to domestic activities are non-toxic. The waste produced by households, shops, offices, restaurants and schools that do not pose a serious problem to animals, plants or to the environment are called Non-toxic Waste.
Sources of Waste:
Depending on their source of origin, wastes are classified into:
1. Domestic Waste:
Wastes generated due to domestic activities are called domestic wastes. Food leftovers, fruits and vegetable peels, bits of paper, packets, polythene bags, bottles, empty metal, aluminium cans, scrap metals, glass pieces, cotton, rags, discarded clothes, ashes from burning coal, sewage from toilets, batteries expired medicines, chemicals, etc., are some of the examples of domestic wastes.
2. Industrial Waste:
Wastes from various types of small arid large scale industries are called industrial wastes. Industrial wastes include any material that is rendered useless during a manufacturing process.
E.g. in a textile industry, wastes may be in the form of fibres used to wipe off oil. Industrial wastes include chemicals (lead, mercury, arsenic, etc.), paints, sandpaper, paper products, industrial by-products, metals, etc.
Industries use a great deal of fuels for energy and produce waste gases and other materials. Sulphur dioxide and nitrogen oxides emitted from power stations cause acid rain and health hazards.
Industrial waste can be categorized on the basis of different industries and their products:
Include tailings, slag heaps and debris. Some mining processes use large volumes of chemicals or liquids.
Mining operations cause leaching of metals into the acidic effluents, thus adding to the metal content to rivers, lakes and groundwater.
(ii) Cement Industry:
Produce various coarse and fine particles.
(iii) Oil Refineries:
It includes inorganic sulphur compounds, hydrocarbons and organic acids.
(iv) Construction Sites:
It includes bricks, pipes, plastic, roofing, insulating materials, asbestos pieces, etc.
(v) Food Processing Units:
Remnants, waste products of dairies, breweries and meat processing units produce organic wastes.
(vi) Paper Industry:
Wood chips, cellulose fibres and chemicals are rejected as waste material. These effluents are highly poisonous and contain chlorine, sulphur dioxide, etc.
(vii) Textile Industry:
Effluents emanate from boiling and processing of fibres.
(viii) Chemical Industries:
Include manufacturing industries, alkali manufacturing, fertiliser, pesticides and several other industries, effluents having phosphorus, fluorine, silica and suspended solids are corrosive.
(ix) Metal Industries:
Effluents containing copper, lead, chromium, cadmium, zinc, etc. These wastes also contain acids, oils, greases and cleansing agents.
3. Agricultural Waste:
Agriculture wastes include the following:
(i) Plant Remains or Crop Residue:
There are two types of crop residues:
(a) Field Residues:
These are the materials left in an agricultural field or orchard after harvesting the crop.
(b) Process Residues:
These are the materials left after processing the crops into useful products.
(ii) Animal Waste:
These include excreta of animals, animal slurry and animal bedding such as poultry litter. Slurry collected from pig contain a chemical which when applied as fertiliser contaminates the soil.
(iii) Processing Waste:
It includes the waste produced by agro-based industries like sugar, dairy, edible oil, food processing, coir setting, pulp and paper.
E.g. in the production of sugar, the extracted sugarcane juice is subjected to a series of purification recesses for making it free from dirt, colour and organic matter. In this purification process, the solid waste, so separated is known as press mud.
Agricultural fertilisers have nitrogen, phosphorus or potassium. These chemicals can affect the surface water during drainage and storm run-off.
(v) Pesticides and Insecticides:
DDT and aldrin have a high persistent capacity, and their residue remains for long periods affecting humans and animals directly or through the food which they consume.
4. Municipal Waste:
Municipal waste is the waste generated in a municipality or a local government area. Such waste is produced by shops, offices, restaurants, schools, courts, libraries, banks, hospitals, parks, etc. and is collected from public waste bins and include household or domestic waste.
Foul smelling liquid waste rich in organic matter and nitrogen compounds, untreated sewage can have serious effects on the ecosystem.
(ii) Degradable and Non-degradable Wastes:
Municipal wastes generated in various offices include used paper cuttings, Xerox paper bits, carbon papers, type writer ribbons, broken pens, pencil shavings, groundnut husks, paper packets, tissue papers, wrappers, glass pieces, rubber, cotton pads, bottles, vegetable matter cooked items, etc.
Municipal, domestic and agricultural solid wastes that can be degraded by microorganisms are called degradable or biodegradable wastes. Vegetable wastes, stale food, tea leaves, egg shells, dry leaves, etc.
Biodegradable wastes can be further classified into:
(i) Simple Biodegradable Waste:
These wastes are easily broken down by natural processes of decomposition. Leaves vegetable peels, plant remains, faecal remains, waste water, dead plants and animals all belong to this category.
(ii) Complex Biodegradable Waste:
The waste material that comes under this category is not easily decomposed. They are resistant to natural processes of decomposition However, over a long period of time, they can be decomposed.
E.g. glass bottles take a million years to decompose, leather shoe take 30-40 years, tin cans take 50-100 years.
Biodegradable wastes can easily serve as alternate sources of energy. Gobar gas and biogas, are an example of conversion of biodegradable wastes into energy.
Non-degradable wastes are the wastes which cannot be degraded or broken down through microbial activities. Such wastes include crude petroleum, plastics, Styrofoam products, cans, glasses, polymer, synthetic pesticides, radioactive fall-out, some industrial effluents and metals like lead. It persists in the environment for a long time, get biomagnified, become toxic and cause health problems.
5. Bio-Medical Wastes:
Bio-medical wastes are the wastes that are generated during the diagnosis, treatment and immunization of human beings or animals. It also includes the waste generated during research and experimentation on animals as well as microbiological waste such as laboratory cultures, micro-organisms, human and animal cell cultures and toxins.
6. Nuclear Waste:
Nuclear waste is the radioactive waste generated from nuclear energy industry, which includes substances used in cooling and storing nuclear fuel, nuclear fuel from reactors in power stations and submarines and X-ray machines in hospitals and airports.
Radioactive elements such as uranium and radium have highly unstable atomic nuclei, whose disintegration results in radiation emission which may be highly injurious.
The leakage of nuclear radiations from nuclear reactors and nuclear research laboratories is a significant source of nuclear radiation.
Impact of Waste Accumulation:
With the use-and-throw concept and mindless consumption, generated waste has increased alarmingly, both in quantity and complexity.
Accumulated solid wastes when left unattended, start decomposing. A number of pathogenic bacteria, virus and fungi grow in such conditions.
i. Spoilage of Landscape:
Much of the world’s solid waste is dumped onto vacant land to decompose. Open dumps not only ruin the natural beauty of the land but also provide a home to rats and other disease carrying organisms.
Both open dumps and landfills may contain poisonous substances that seep into the groundwater or flow into streams and lakes.
The word “pollute” means to degrade or to make dirty. Accumulation of waste is probably the most visible form of pollution.
Agriculture and the food processing industry are considered to be the largest contributors to the total annual production of solid wastes.
iii. Health Hazards:
Spread of Disease through Contamination:
Several incidents around the world have demonstrated the potential harm of accumulation of waste on human health.
Unattended waste dumped in the open, attracts flies, rats and other creatures that act as vectors of the diseases and spread them among human beings.
Domestic waste poses a serious threat since it is organic in nature. It undergoes fermentation and creates conditions favourable to the survival and growth of pathogens.
Waste dumped near a water source percolates through the soil into the water bodies and contaminates the water.
Direct dumping of untreated waste in rivers, seas and lakes results in the accumulation of toxic substances in the water bodies and further in the food chain (bio-magnification).
Choking of drains and gully pits by the solid wastes results in water logging, especially during the rainy season. This leads to breeding of mosquitoes and spread of diseases like malaria and chikungunia.
iv. Effect on Plants:
Waste accumulation has dangerous effect on plant life directly by deposition of harmful toxins from wastes or indirectly through soil.
The toxins can cause:
(i) Leaf injuries and reduction in the rate or photosynthesis
(ii) Premature leaf fall
(iii) Decrease in transpiration
(v) Reduction in biological nitrogen fixation
v. Effect on Animals and Birds:
The wastes consumed can lead to many diseases. The plastics consumed can choke the animal and may even result in death. With increased levels of toxins in the body, eggs will have defective shell, reproducing ability reduces and their offsprings may develop birth defects and have high mortality rate.
vi. Effect on Aquatic Life:
Waste accumulation can cause significant damage to aquatic life, both fresh water and marine.
Two categories of waste that cause greatest damage to aquatic life are — pesticides run off from agricultural lands and industrial and domestic wastes that are improperly disposed of into water bodies.
Diseases due to Contamination:
Common diseases spread by mosquitoes, flies, rodents and pet animals.
Typhoid, diarrhoea, dysentery, cholera, gastro-enteritis, etc.
Kala-azar, sandfly fever, etc.
3. Tsetse Fly:
Malaria, filaria, yellow fever, dengue, chikungunya, encephalitis, Zika fever etc.
Plague, salmonellosis, etc.
6. Pet Animals:
Rabies, Hydrated diseases, etc.
Dermatophytosis, anthrax, etc.
Common Water-Borne Diseases:
Viral Hepatitis, diarrhoea, etc.
Cholear, typhoid, dysentery.