We studied the relationship between water flux of a UF membrane with MLSS, soluble COD, and the viscosity of activated sludge suspension in a human excrement treatment test plant utilizing UF membrane. The bench-scale plate and frame UF membrane test unit was operated for activated sludge suspension of 20 approximately 29 kg/m3 MLSS, 500-730 g/m3 soluble COD and 0.38-1.3 Pa.s viscosity under the conditions of 0.2-0.24 MPa average pressure and 2 m/s recirculating velocity. As a result, stable-state water flux was 0.55-1.65 m/D at 25-degrees-C. The relationship between filtration resistance R to transmembrane pressure drop DELTA-P, MLSS, COD, and viscosity-eta was expressed by the following equation: R = 842.7 DELTA-P (MLSS) 0.926(COD)1.368(eta)0.326. From this equation, we were able to predict R with an accuracy of +/- 24%. Soluble COD had the largest effect lon water flux followed by MLSS. The effect of viscosity was relatively small.
