BIOLOGICAL PHOSPHORUS UPTAKE IN SUBMERGED BIOFILTERS WITH NITROGEN REMOVAL

This paper introduces biological phosphorus removal (Bio-P) from waste water on a submerged biofilter. Pilot scale research was carried out o ver a period of two years using a floating upflow aerated filter, orig inally designed for nitrification and denitrification of sewage. The f actors which influence Bio-P on fixed film processes and the possible biofilter configurations which eliminate C, N and P are discussed. The procedures are applicable to all types of treatment plants using biof ilters, both new and already in existence, making no distinction betwe en the different processes available today, co-current and counter-cur rent filters. Biological phosphorus removal can be associated to the d ifferent treatment levels required : organic matter removal; secondary nitrification secondary nitrification and denitrification. For the th ird option - complete nutrient removal, treatment is completed with a hydraulic retention time in the filter bed of under four hours. Becaus e of the simultaneous filtration with effluent SS below 10 mg/l, low p hosphorus residuals can be achieved by Bio-P alone. The modifications required for setting up this operating procedure on any treatment plan t are presented.