Study on the factors affecting coagulation and flocculation in treatment of industrial effluents

摘要

The introduction of wastewater treatments increases the plant cost; therefor any attempt to improve their efficiency is valuable. The industrial liquid effluents are very difficult to generalize. Their characteristics not only vary with the type of the industry, but also from plant to plant producing same type of end products. Coagulation and flocculation can achieve the effective removal of suspended particles. Operating within the optimum parameters will reduce the cost of treatment and will increase the quality of the water. The objectives of the study were, to compare the effectiveness of different coagulants, to determine their optimum dosage, and the optimum pH. In the present study "Jar Test" was used. Samples from Pulp and Paper, and Textile effluents were used. The following coagulants were used: ferric chloride, ferrous sulphate, aluminium sulphate, and combination of them. Aluminium sulphate was regarded as the best coagulant since it achieved 98% solids removal for pulp and paper effluent and 95% for textile effluent at pH=7. With the combination of aluminium sulphate and ferric chloride the turbidity of 1.83 NTU was achieved for pulp and paper effluent, compared with 74.5 NTU from the industry. For the textile effluent 6.01 NTU turbidity was achieved.