Industrial wastes are divided into two types:

$(i)$ Biodegradable waste : Biodegradable wastes are genereted by cotton mills, food processing units, paper mills and textile factories.

$(ii)$ Non-biodegradable wastes : Non-biodegradable wastes are generated by thermal power plants which produce fly ash; integrated iron and steel plants which produce blast furnace slag and steel melting slag. Industries manufacturing aluminium, zinc and copper produce mud and tailings. Fertilizer industries produce gypsum. Hazardous wastes such as inflammables, composite explosives or highly reactive substances are produced by industries dealing in metals, chemicals, drugs, pharmaceuticals, dyes, pesticides, rubber goods etc.