Wool scouring waste treatment by a combination of coagulation–flocculation process and membrane separation technology

Wool scouring produces a highly polluting effluent. This study discusses a process based on a combination of coagulation–flocculation process followed by a membrane separation technology to improve the removal efficiency. The optimum operating conditions for the coagulation–flocculation process were pH 4 and 500 mg/L in ferric chloride. Under these conditions, the settled liquor was treated with ceramic and polymeric membranes of various molecular weight cut-offs (MWCO). Rejection of total organic carbon (TOC) reached a maximum value of 86% for a 0.3 kDa MWCO polymeric membrane. Membrane fouling was more significant in the ceramic membranes than the polymeric ones. High quality permeate effluent was obtained by operating in a batch retentate-recycling mode for a 0.3 kDa MWCO membrane. A mathematical model permits estimates of TOC concentrations in the retentate and permeate obtainable by working in the batch retentate-recycling mode with different MWCO membranes.