|SIMSEK, HALIS - North Dakota State University|
|KASI, MURTHY - Moor Engineering, Inc|
|MURTHY, SUDHIR - District Of Columbia Water & Sewer Authority (DCWASA)|
|KHAN, EAKALAK - North Dakota State University|
Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2016
Publication Date: 1/22/2016
Publication URL: http://handle.nal.usda.gov/10113/61961
Citation: Simsek, H., Kasi, M., Ohm, J.-B., Murthy, S., Khan, E. 2016. Impact of solids retention time on dissolved organic nitrogen and its biodegradability in treated wastewater. Water Research. 92:44-51.
Interpretive Summary: Dissolved organic nitrogen (DON) in wastewater has recently gained attention because DON potentially stimulates algal growth and consequently, causes depletion of oxygen in water that has harmful effect on aquatic life in estuaries, lakes, and coastal waters. Wastewater treatment facilities use an activated sludge process to remove nutrients including DON in treatment of wastewater. Laboratory scale experiment was conducted to examine whether different solid retention times (SRTs) in activated sludge process could be used to control DON levels in treated wastewater. The minimum DON value in treated wastewater was 4.75 mg/L at 0.3-day SRT and the maximum value was 8.08 mg/L was at 7-day SRT. The DON levels in treated wastewater showed decreasing trend after 4 day SRT. This study indicates the benefit of high SRTs in term of producing treated wastewater with less DON biodegrability which would lead to relatively less oxygen consumption and nutrient support in receiving water.
Technical Abstract: Dissolved organic nitrogen (DON) and its biodegradability in treated wastewater have recently gained attention because DON potentially causes oxygen depletion and/or eutrophication in 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. Actual primary treated wastewater was used to feed the chemostat reactor. Results indicated that there was no trend between effluent DON and SRTs. The minimum and maximum effluent DON values were 4.75 mg/L (at 0.3-day SRT) and 8.08 mg/L (at 7-day SRT), respectively. Effluent BDON was comparable for SRTs of 0.3 to 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. This study indicates the benefit of high SRTs in term of producing effluent with less DON biodegrability which would lead to relatively less oxygen consumption and nutrient support in receiving waters.