Waste is an unwanted or discarded material that can not be used in its present form. Waste can be classified into the following categories:
(1) Industrial solid waste
The major producers of solid waste are:
• Thermal power plants producing coal ash/ fly ash;
• The integrated iron and steel mills producing blast furnace slag;
• Non-ferrous industries like aluminium, copper and zinc producing red mud and tailings;
• Sugar industries generating press mud;
• Pulp and paper industries producing lime mud;
• Fertilizer and allied industries producing gypsum;
• Hospitals producing bio-medical waste.
(2) The major producers of liquid effluents
2. Thermal power plants
3. Iron and steel
4. Fertilizer 13. Pesticides
5. Zinc Smelters
6. Copper smelters
7. Aluminium smelters
8. Oil refineries
10. Pulp and Paper
12- Dyes and dye intermediates
16. Sugar and
17. Basic drugs
(3) Municipal solid waste
Vegetable rejects from domestic units and vegetable markets, plastic material, building debris, bio-medical waste etc.
(4) Industrial liquid waste
There is hardly an industrial process that does not generate liquid effluents. Often these are discharged into the rivers or streams without any treatment. As a result, these effluents pollute the river that adversely affects aquatic life and the river ecology. The industrial wastewaters often contain valuable materials that can be recovered. This approach improves the quality of effluent discharged into the river, on one hand, fetches additional income to the industry on the other hand.
(5) Municipal liquid waste
Sewage from hotels and residential colonies.
(6) Gaseous waste
Various gases are emitted from industrial installations that have the potential use but are not being utilized. For example, the Oil and Natural Gas Commission (ONGC) is flaring gas worth Rs 750 crores per annum. This can be converted into methanol and petrol. Carbon dioxide emitted from various sources can be used to produce calcium carbonate. Sulphur dioxide emitted can be converted into either elemental sulphur or gypsum. Waste heat from hot gaseous emissions can be recovered for suitable use.
(7) Radio-active waste
Most of such waste is generated from nuclear power plants. The waste is highly hazardous to live animals and hence needs careful planning for its disposal and treatment.
Categories of Waste
Wastes are divided into the following two categories according to their hazard potential:
(i) Hazardous waste:
These belong to a special category of wastes containing certain chemicals, metals, and pathogenic organisms that can cause serious health problems and damage to the environment even at low concentration. Indiscriminate disposal of these wastes into the environment without proper treatment could lead to complex hazardous pollution of river water, land and groundwater resources.
(ii) Non-hazardous waste:
All other wastes which are not covered under the hazardous category are included in this group.