TERTIARY-TREATMENT OF URBAN WASTE-WATER BY CROSS-FLOW MICROFILTRATION

Using cross flow microfiltration as a tertiary treatment would make the treatment reliable and achieve virtually a total disinfection. However, the use of the membrane techniques is Limited because of the material fouling. Our results show that the fouling mechanisms depend on the choice of the secondary upstream process. The quality of the effluent and the permeate flux obtained are very different if the sewage has been treated by a biological or by a physico-chemical process. The operating conditions of these processes have also an influence on the variations of the membrane permeability. In particular we have observed the importance of the load in the case of an activated sludge process and the role of the coagulant dose in the case of a physico-chemical process. The supracolloidal fraction of the suspensions seems to be one of the main fouling reasons.