Reuse of waste water for industrial cooling systems

Abstract

Reuse of municipal effluent for cooling systems in a large refinery and petrochemical complex is described. Quality criteria for the cooling water were related to scale formers, corrosion, and biogrowth. After tertiary lime treatment using sludge blanket precipitator-clarifier was applied, phosphate removal, high reductions in alkalinity, calcium, COD, and suspended solids were obtained. A stripping tower reduced ammonia concentrations by 50%. Biological nitrification eliminated ammonia in the circulating cooling system. Acidity generated by nitrification neutralized excess lime in treated effluent. Reclamation of waste water for cooling saved millions of cubic meters of fresh water.