Anaerobic Biofiltration versus Aerobic Membrane Filtration: Comparison on a Difficult Substrate
Several methods were compared to treat heat treatment liquor on a municipal wastewater treatment plant, to reduce loading and allow upgrading. To ensure low suspended solids in the return flows, granular anaerobic filters were chosen in parallel with membrane treatment:–an upflow wood-based charcoal anaerobic filter–an upflow floating polystyrene anaerobic filter–an aerobic reactor (activated sludge) coupled with microfiltration. Very similar loading rates and removal efficiency was obtained with the anaerobic filters; they allow to treat highly concentrated effluents in a detention time of 10 h but COD removal efficiency was limited to 60%. The higher contact time of up to 7 days in aerobic treatment, coupled with microfiltration, achieves elimination of 85% of COD and 95% of BOD. Nevertheless, loading rates and biomass concentrations remained low and flux on the membranes was heavily restricted.