Definition. Liquid industrial waste is any aqueous or non-aqueous liquid discharge generated by an industrial or manufacturing process — process water, wash-down water, spent process chemicals, cooling water blowdown — that is not intended for the final product and requires management or treatment before discharge, distinct from ordinary domestic sanitary sewage.
Three examples with widely varying characteristics:
Food/cannery processing wastewater. High BOD5 and suspended solids from organic process residues, but generally low toxicity and readily biodegradable.
Metal-finishing/electroplating rinse water. Low BOD5 but high dissolved heavy-metal concentration (chromium, nickel, zinc, cyanide) and significant acute toxicity — essentially the opposite profile from food-processing waste.
Pulp-and-paper mill effluent. High colour, dissolved and suspended solids, and chlorinated organics (AOX) from the bleaching process, with a very different treatment demand (colour removal, AOX minimization) than either of the above.
