Comparative study of the effectiveness of chemical coagulants used in effluent treatment of Garment washing industry in Sri Lanka

Industries in particular generate enormous amount of wastes which can cause serious pollution in the environment. Water pollution mainly occurs due to the presence of dissolved inorganic materials, organic materials, other substances found in domestic and industrial wastewater and their subsequent products. The main objective of the wastewater treatment is to dispose the treated effluent without causing an adverse impact on the ecosystem of receiving water body and the compliance with stipulated norms and standards. In chemical treatment, chemicals i.e coagulants are added to waste water. Coagulation or destabilization of a colloidal suspension results in joining of minute particles through physical and chemical processes. Most commonly used coagulants for chemical treatment in Sri Lanka are Alum, Ferrous sulphate, Ferric Chloride & Poly Aluminium Chloride (PAC). The main objective of this study is to identify the best coagulant for chemical treatment by means of maximum Chemical Oxygen Demand (COD) removal efficiency, minimum post treatment environmental impacts and cost effectiveness in Garment washing effluent treatment. Garment washing effluent was selected for this study because these industries are located in low lying marshy areas, urban mixed residential areas and even in domestic level without having required disposal facilities.