Collaborative research: impact of wastewater derived organic nitrogen on eutrophication

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0932665/0932632 Gu/Paerl Many municipal wastewater treatment facilities are facing increasingly stringent effluent N limits that are near or beyond the current limits of technology. Removal of dissolved organic nitrogen (DON) becomes necessary if the permitted N level is below the limit of conventional N removal technology. The capital cost required to research and install advanced treatment technologies for further removal of the residual DON is substantial. Current regulations use total nitrogen for setting limits without consideration of the possibility that DON and inorganic N may differ in their bioavailability to phytoplankton and therefore their potential harmful impact on receiving aquatic systems. The question arises on whether further reduction of DON will bring substantial environmental benefits relative to the significant cost incurred, given the uncertainty over the bioavailability of wastewater derived DON (wwDON). Currently, there is little information on the wwDON bioavailability to phytoplankton in receiving waters and there is no accepted method for quantitatively assessing the wwDON bioavailability. This study proposes to addresses this issue and fill in the knowledge gap for understanding the impact of wastewater derived organic nitrogen on receiving aquatic ecosystems. The proposed research aims at investigating the characteristics of wwDON from municipal treatment facilities and assessing the bioavailability of wwDON to phytoplankton and its impact on eutrophication. Although N is usually limiting for saline waters, both saline waters and freshwaters are of concern here because most municipalities discharge to freshwaters, and recent studies indicated that the fate and lability (labile) of N in upstream freshwater systems will eventually affect the transport of N and nutrient condition in down-stream N-sensitive estuary and coastal systems. The specific objectives are: 1. Assess the bioavailability of wwDON to two phytoplankton species known to play roles in eutrophication. 2. Investigate the bioavailability of wwDON to both saline and freshwater phytoplankton and the role of bacteria in labilization of wwDON to algae. 3. Examine the relationship between the composition of wwDON and its bioavailability, and identify the fractions of wwDON that are bioavailable versus recalcitrant. 4. Further evaluate the fate and bioavailability of wwDON to natural biota (including both algae and bacteria) using 15N-labeled wwDON produced in situ. The project will demonstrate the benefits of interdisciplinary and integrated approach for solving environmental challenges. The multidisciplinary research covers expertise in at least three disciplines that will apply unique, comprehensive, and state-of-the-art assessment of the bioavailability of wwDON to freshwater aquatic systems. The proposed research addresses a pressing issue with significant social and economical impacts that have not previously been investigated. The results will provide essential information and framework for developing a standard wwDON bioavailability assessment method that are urgently needed by utilities and regulators in order to target their treatment design and investments at eliminating the N components that are truly harmful to receiving aquatic ecosystems and therefore maximizing the environmental benefits. The project will enhance both existing and new education outreach programs at the two institutions. At NU, there is BEST (Biotechnology for the Environment, Showcase and Training), a center recently initiated by Gu; CONNECTIONS and RET, two NSF funded education programs; and CO-OP, a distinguished experiential learning program for NU. At UNC, there are NSF-supported (Ecosystems, EID and Ocean Sciences Programs) summer internships at UNC-IMS and NSF-supported Summer Pre-graduate Research Experience Program (SPGRE). All these programs intend to attract and involve students from diverse backgrounds. The PI started ITRI (Industrial Translational Research Initiative) and will work with WEF/WERF (Water Environment Federation) for information dissemination to professionals and practitioners via web-based tools and databases