TREATMENT OF MUNICIPAL WASTEWATER BY A MEMBRANE BIOREACTOR: RESULTS OF A SEMI-INDUSTRIAL PILOT-SCALE STUDY

Membrane bioreactors (MBR) represent a new generation of processes that can be applied to the treatment of municipal and industrial wastewater. Their main advantage is their ability to keep all biomass in the bioreactor, thus removing all suspended solids from the treated water and disinfecting it according to the membrane cut-off threshold. Perfect control as well as separation of hydraulic (HRT) and biomass retention times (SRT) also means better control of biological activity. Treatment of municipal wastewater on a semi-industrial aerobic pilot-scale MBR (HRT: 24 hr; SRT: 25 days) resulted in complete nitrification and from 93 to 99.9% removal of COD, N-NH 3 and suspended solids. The COD removed loading rate was equal to 0.2 kg/kg VSS.day and the average sludge production was around 0.2 kgSS/kgCOD. Filtration through 0.1 µm ceramic hollow fibres (Surface = 1.1 m 2 ) under moderate conditions (1.5 to 3.5 m/s; TMP