Experimental investigation of adsorption-flocculation-microfiltration hybrid system in wastewater reuse

Membrane hybrid systems are becoming increasingly important as cost effective solutions in wastewater treatment and reuse. The effect of pretreatments namely floating medium flocculation (FMF) and powdered activated carbon (PAC) adsorption on organic and phosphorus removal was studied. The FMF was found to increase the phosphorus removal up to 97%. This preflocculation improved the dissolved organic removal only marginally (from 20% to 40%) whilst the pretreatment of adsorption increased the organic removal to more than 98%. The decline in filtration (permeate) flux of microfiltration was reduced by the incorporation of these pretreatment methods. Detailed studies on the effect of PAC dose indicated that a PAC dose of 1 g/L was the optimum in terms of organic removal and filtration flux. PAC doses in excess of 1 g/L contributed to a significant decrease in filtration flux. The critical flux was experimentally evaluated for crossflow microfiltration (CFMF) with and without the pretreatment. The pretreatment of adsorption led to six times higher critical flux than that without any pretreatment. The preflocculation alone did not significantly increase the critical flux. There was only a 33% increase with preflocculation. However, the preflocculation combined with PAC adsorption resulted in nine times higher critical flux. The results showed that a pretreatment of flocculation and adsorption led to almost complete phosphorus and organic removal while reducing the membrane clogging. (C) 2004 Elsevier B.V. All rights reserved.