Membrane bioreactors and their role in wastewater reuse

The potential of membrane aeration bioreactors (MABR), biological aerated filters (BAF) and membrane bioreactors (MBR) for grey water recycling has been evaluated. The MBR demonstrated the highest efficacy towards grey water recycling in terms of the three main water quality determinants of CBOD5, turbidity and total coliforms, providing 100% compliance in all cases. The membrane provided a solid free effluent and a biological culture adapted to treat the relatively difficult to degrade fractions of the grey water. The initial flux rate through the system was 28 l m−2h−1, which then gradually decreased to a stable level of 8 l m−2h−1. This demonstrated the process to be operating under sub critical flux conditions where no irreversible fouling occurs. Volumetric loading rates were correspondingly low due to the low flux rates and the weak strength of grey water, but process efficacy remained high throughout the loading rate range of 0.005–0.11 kgBOD m−3d−1 employed. The MBR was seen as particularly suitable as it was very effective at stabilising influent water quality variations and acted as a disinfection barrier to the water, providing a disinfection mechanism.