Nutrient balances for combined nitrification and denitrification in biofilters

Nutrient balances were set up for a biofiltration pilot plant operated with pre-denitrification and post-nitrification in order to gain more informati on about its treatment efficiency. Data collected during several weeks was used for balancing the parameters phosphorus (P-tot), carbon (COD) and nitr ogen (N-tot). From the results obtained (overall deviation of 20-30%) it ca n be stated that 30% of the phosphorus load in the inlet was incorporated i nto biomass or sludge. The effluent contained between 50 and 80% of the inc oming phosphorus loading. The percentage of the initial carbon loading foun d by sludge analysis was in the range of 60 to 80% and about 20% were measu red in the effluent. Thus, only 20 to 40% were oxidized and/or utilized as carbon source for denitrification. The nitrogen balance showed similar valu es for incorportion as determined for phosphorus (20-40%). As not more than 20% of the incoming nitrogen load could be denitrified, 40-60% left the pl ant with the effluent.