DESIGN OF WASTEWATER TREATMENT PLANTS USING SUBMERGED BIOLOGICAL FILTERS FOR NITROGEN REMOVAL
Two concepts for nitrogen removal using submerged biological filters are discussed, namely pre-denitrification followed by combined precipitation and pre-precipitation followed by post-denitrification. The preliminary design basis is presented, together with a design example and cost figures. Pre-denitrification is the preferred method for moderate nitrogen removal efficiencies (<60-70 %) and wastewater with normal concentrations and C/N-ratios. Post-denitrification is required for high nitrogen removal efficiencies (>70 %) or if the wastewater is very dilute or has a low C/N-ratio.