Abstract
Membrane separation technology has been applied for the solid-liquid separation of activated sludge in high-rate denitrification processes employed for the treatment of night soil. It renders the system capable of maintaining high concentration of microorganisms in activated sludge process. A parameter of great importance in the membrane separation is to maintain the designed flux for discharging the expected daily volume of effluent. Performance of a tubular type polyolefin membrane was evaluated in this study. The test results based on the flux date in the bench scale and pilot plant tests reveal that low-pressure operation was more favourable than the high-pressure operation for separating activated sludge. After extended periods of operation, the membrane was coated with scale composed of calcium carbonate, phosphate and similar materials. Types of coagulants used for coagulating the sludge had an important effect on the flux. Alkaline sodium hypochlorite solution and citric acid were remarkably effective as cleaning chemicals.
