Bioavailable and biodegradable dissolved organic nitrogen in activated sludge and trickling filter wastewater treatment plants

Authors: SIMSEK, HALIS - North Dakota State University; KASI, MURTHY - Moor Engineering, Inc; Ohm, Jae-Bom; BLONIGEN, MARK - City Of Fargo Wastewater Treatment Plant; KHAN, EAKALAK - North Dakota State University

Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2013
Publication Date: 3/26/2013
Publication URL: http://handle.nal.usda.gov/10113/57868
Citation: Simsek, H., Kasi, M., Ohm, J.-B., Blonigen, M., Khan, E. 2013. Bioavailable and biodegradable dissolved organic nitrogen in activated sludge and trickling filter wastewater treatment plants. Water Research. 47:3201-3210.

Interpretive Summary: Current regulations for total nitrogen in water after clarification in wastewater treatment facility (WWTF) are approximately 5 mg nitrogen/L or less in USA. Specifically, dissolved organic nitrogen (DON) is known to contribute to eutrophication that generally increases growth of algae and results in a severe degradation of water quality. Bacteria are known to degrade DON that promotes algae growth in water. A study was carried out to understand the fate of biodegradable DON (BDON: DON that can be degraded by bacteria) and bioavailable DON (ABDON: DON that can be used by algae) along the treatment trains of two WWTFs equipped with an activated sludge (AS) system and a WWTF equipped with a two-stage trickling filter (TF) process. A bacterial mixture was used for BDON determination, while a pure cultured algal inoculum (Selenastrum capricornutum) and a combination of the bacterial and alga inocula were used for ABDON determination. Results show that BDON and ABDON varied significantly within the treatment facility and between the two facilities. The TF facility removed about 65% of BDON and up to 63% of ABDON while the AS facility removed about 68% of BDON and up to 56% of ABDON. For the TF facility, BDON and ABDON were 62% and 71% of DON, while they were 26% and 47% of DON for the AS WWTF after wastewater treatment, respectively. BDON and ABDON results further showed that some portions of DON are utilizable by bacteria only or algae only while there is a portion of DON utilizable by either bacteria or algae. DON utilization was the highest when both bacteria and algae were used as a co-inoculum in the samples. This study is the first to investigate the fate of BDON and ABDON along the treatment trains of two different WWTFs.

Technical Abstract: A study was carried out to understand the fate of biodegradable dissolved organic nitrogen (BDON) and bioavailable dissolved organic nitrogen (ABDON) along the treatment trains of a wastewater treatment facility (WWTF) equipped with an activated sludge (AS) system and a WWTF equipped with a two-stage trickling filter (TF) process. A mixed culture bacterial inoculum was used for BDON determination, while a pure cultured algal inoculum (Selenastrum capricornutum) and a combination of the bacterial and alga inocula were used for ABDON determination. Results show that BDON and ABDON varied significantly within the treatment facility and between the two facilities. From after primary clarification to final effluent, the TF facility removed about 65% of BDON and up to 63% of ABDON while the AS facility removed about 68% of BDON and up to 56% of ABDON. For the TF facility, BDON and ABDON were 62% and 71% of the effluent dissolved organic nitrogen (DON), while they were 26% and 47% of the effluent DON for the AS WWTF. BDON and ABDON results further showed that some portions of DON are utilizable by bacteria only or algae only while there is a portion of DON utilizable by either bacteria or algae. DON utilization was the highest when both bacteria and algae were used as a co-inoculum in the samples. This study is the first to investigate the fate of BDON and ABDON along the treatment trains of two different WWTFs.