Fate of Bioavailable and Biodegradable Dissolved Organic Nitrogen in a Two-Stage Trickling Filter Wastewater Treatment Plant

Biodegradability and bioavailability are two important fractions of effluent dissolved organic nitrogen (DON) as they can support bacterial and algal growth in the receiving waters. Biodegradable DON (BDON) is the portion of DON that can be mineralized by an acclimated mixed bacterial culture. Bioavailable DON (ABDON) could support the growth of algae in the receiving waters. A study was carried out to understand the fate of BDON and ABDON along the treatment trains of a wastewater treatment facility (WWTF) equipped with an activated sludge (AS) system and a WWTF equipped with a trickling filter (TF) process. Results show that BDON and ABDON varied significantly within the treatment facility and between the two facilities. The TF facility removed about 76% of influent BDON and up to 88% of influent ABDON, while the AS facility removed about 65% of influent BDON and up to 64% of influent ABDON. For the TF WWTF, BDON and ABDON were 65% and 61% of the effluent DON, while they were 35% and 38% of the effluent DON for the AS WWTF.