title: Formation of Low-Molecular-Weight Dissolved Organic Nitrogen in Predenitrification Biological Nutrient Removal Systems and Its Impact on Eutrophication in Coastal Waters.
abstract: To alleviate eutrophication in coastal waters, reducing nitrogen (N) discharge from wastewater treatment plants (WWTPs) by upgrading conventional activated sludge (CAS) to biological nutrient removal (BNR) processes is commonplace. However, despite numerous upgrades and successful reduction of N discharge from WWTPs, eutrophication problems persist. These unexpected observations raise the possibility that some aspects of BNR yield environmental responses as yet overlooked. Here, we report that one of the most common BNR processes, predenitrification, is prone to the production of low-molecular-weight dissolved organic N (LMW-DON), which is highly bioavailable and stimulates phytoplankton blooms. We found that in predenitrification BNR, LMW-DON is released during the post-aerobic step following the preanoxic step, which does not occur in CAS. Consequently, predenitrification systems produced larger amount of LMW-DON than CAS. In estuarine bioassays, predenitrification BNR effluents produced more phytoplankton biomass than CAS effluents despite lower N concentrations. This was also supported by stronger correlations found between phytoplankton biomass and LMW-DON than other N forms. These findings suggest that WWTPs upgraded to predenitrification BNR reduce inorganic N discharge but introduce larger quantities of potent LMW-DON into coastal systems. We suggest reassessing the N-removal strategy for WWTPs to minimize the eutrophication effects of effluents.
authors.affiliation: Department of Civil and Environmental Engineering, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors.forename: Heonseop
authors.initials: H
authors.lastname: Eom
authors.affiliation: Springfield Water and Sewer Commission , Springfield, Massachusetts 01001, United States.
authors.forename: Douglas
authors.initials: D
authors.lastname: Borgatti
authors.affiliation: Institute of Marine Sciences, University of North Carolina , Chapel Hill, North Carolina 28577, United States.
authors.forename: Hans W
authors.initials: HW
authors.lastname: Paerl
authors.affiliation: Department of Civil and Environmental Engineering, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors.forename: Chul
authors.identifier: 0000-0003-0695-8562
authors.initials: C
authors.lastname: Park
mesh_terms: D005068:Eutrophication; D009584:Nitrogen; D012722:Sewage; D014865:Waste Disposal, Fluid; D062065:Wastewater
chemical_list: D009584:Nitrogen; D012722:Sewage; D062065:Wastewater