Treatment of Cooling Tower Blowdown

Cooling tower blowdown can contain zinc and chromates which must be removed prior to discharge into the environment. Treatment alternatives include chemical reduction, ion exchange, and electrochemical reduction. A novel process involves lime softening with recycle of the treated water to the cooling water system. The best technology to utilize is a function of cooling-water quality. If makeup water is high in hardness, lime softening may be most appropriate. The ion exchange process functions best in water low in dissolved and suspended solids. The chemical and electrochemical processes can function well irrespective of cooling water chemistry.