TREATMENT OF MUNICIPAL WASTE-WATER BY A MEMBRANE BIOREACTOR - RESULTSOF A SEMIINDUSTRIAL PILOT-SCALE STUDY

Membrane bioreactors (MBR) represent a new generation of processes tha t can be applied to the treatment of municipal and industrial wastewat er. Their main advantage is their ability to keep all biomass in the b ioreactor, thus removing all suspended solids from the treated water a nd disinfecting it according to the membrane cut-off threshold, Perfec t control as well as separation of hydraulic (HRT) and biomass retenti on times (SRT) also means better control of biological activity, Treat ment 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-NH3 and suspended solids. The COD r emoved loading rate was equal to 0.2 kg/kg VSS,day and the average slu dge production was around 0.2 kgSS/kgCOD. Filtration through 0.1 mu m ceramic hollow fibres (Surface = 1.1 m(2)) under moderate conditions ( 1.5 to 3.5 m/s; TMP < 2 bars) maintained good flow rates of 60 to 80 1 /hr at 20 degrees C for over 15 days without chemical washing. The per formances shown here over a total period of 100 days emphasize perfect stability of the MBR process in treating municipal wastewater.