Reduction of faecal coliform bacteria in sewage effluents using a microporous polymeric membrane

A study has been undertaken to assess the performance of an extruded, polymeric, tubular, microfiltration membrane with respect to its ability to disinfect and clarify sewage effluents. Membranes of two different pore sizes were investigated and the membrane module operated cyclically with 10 min on and 0.5 min off. Both membranes were seen to be effective at improving the physiochemical properties of the sewage effluents, with significant reductions in suspended solids (SS), chemical oxygen demand (COD) and turbidity. The smaller pore size membrane, however, was more efficient at removing faecal coliform bacteria (FCB) from the effluents with a rejection that was comparable with existing membrane systems. It was seen that breakthrough of FCB occurs at the beginning of a cycle and that removal efficiency quickly rises to a higher and more stable level of removal during the cycle. The performance, with reference to FCB rejection, against the primary effluent was significantly better than for the secondary effluent for the larger pore size membrane.