title: Impact of solids retention time on dissolved organic nitrogen and its biodegradability in treated wastewater.
abstract: Dissolved organic nitrogen (DON) and its biodegradability in treated wastewater have recently gained attention due to increased regulatory requirements on effluent quality to protect receiving waters. Laboratory scale chemostat experiments were conducted at 9 different solids retention times (SRTs) (0.3, 0.7, 2, 3, 4, 5, 7, 8, and 13 days) to examine whether SRT could be used to control DON, biodegradable DON (BDON), and DON biodegradability (BDON/DON) levels in treated wastewater. Results indicated no trend between effluent DON and SRTs. Effluent BDON was comparable for SRTs of 0.3-4 days and had a decreasing trend with SRT after that. Effluent DON biodegradability (effluent BDON/effluent DON) ranging from 23% to 59% tended to decrease with SRT. Chemostat during longer SRTs, however, was contributing to non-biodegradable DON (NBDON) and this fraction of DON increased with SRT above 4 days. Model calibration results indicated that ammonification rate, and growth rates for ordinary heterotrophs, ammonia oxidizing bacteria and nitrite oxidizing bacteria were not constants but have a decreasing trend with increasing SRT. This study indicates the benefit of high SRTs in term of producing effluent with less DON biodegradability leading to relatively less oxygen consumption and nutrient support in receiving waters.
authors: Department of Agricultural and Biosystems Engineering, North Dakota State University, Fargo, ND 58108, USA.
authors: Halis
authors: H
authors: Simsek
authors: HDR, Inc., Boise, ID 83706, USA.
authors: Murthy
authors: M
authors: Kasi
authors: USDA-ARS Hard Red Spring and Durum Wheat Quality Laboratory, Harris Hall, North Dakota State University, Fargo, ND 58108, USA.
authors: Jae-Bom
authors: JB
authors: Ohm
authors: District of Columbia Water and Sewer Authority, Washington, DC 20032, USA.
authors: Sudhir
authors: S
authors: Murthy
authors: Department of Civil and Environmental Engineering, North Dakota State University, Fargo, ND 58108, USA. Electronic address: eakalak.khan@ndsu.edu.
authors: Eakalak
authors: E
authors: Khan
mesh_terms: D000641:Ammonia / Q000032:analysis; D001673:Biodegradation, Environmental; D057919:Biological Oxygen Demand Analysis; D009584:Nitrogen / Q000032:analysis*; D009930:Organic Chemicals / Q000032:analysis / Q000302:isolation & purification; D012995:Solubility; D013997:Time Factors; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D000641:Ammonia; D009584:Nitrogen; D009930:Organic Chemicals; D062065:Wastewater
keywords: Biodegradable dissolved organic nitrogen; Dissolved organic nitrogen; Non-biodegradable dissolved organic nitrogen; Solids retention time; Wastewater