THE ENHANCEMENT OF UPFLOW ANAEROBIC SLUDGE BED REACTOR PERFORMANCE USING CROSS-FLOW MICROFILTRATION

Crossflow microfiltration (CFMF) was used to filter liquor removed from the top of a laboratory-scale upflow anaerobic sludge-bed (UASB) reactor. Prior to filtration the COD removal was 91.7%, with 1.0 g l(-1) of suspended solids at the top of the reactor. During 17 days of operation with filtration the suspended solids concentration was increased to 5.9 g l(-1). The maximum solids concentration at which the reactor could be operated was not reached. The effluent quality was high (0.050 g l(-1) suspended solids). The COD removal was increased to between 98 and 99%. It is possible that returning liquor aerated the top zone of the reactor, promoting the growth of aerobic organisms on residual COD material. Alternatively the increased capacity could have been due to the biomass retention. The coupling of the UASB reactor to the CFMF unit led to an improvement in the effluent from the system, i.e. lower effluent suspended solids concentration and increased COD removal capacity due to aerobic polishing.