Abstract

Flotation has been investigated as an alternative to sedimentation for the purification of tannery waste waters. The method offers a number of advantages and is particularly applicable to the treatment of strong beamhouse wastes from which sulphide has been removed by catalysed aeration or otherwise. With these liquors removals of 70% of the COD (initially 10,000 mg/liter) and nearly 90% of the suspended solids (initially 2500 mg/liter) were obtained, with the generation of compact sludge blankets which were readily amenable to further dewatering. The method is one of very few which can be operated on-site at costs lower than those charged for treating the raw effluent by some Water Authorities. The sludges may have some value as a source of protein for animal feeding.