title: Enrichment of15N/14N in wastewater-derived effluent varies with operational performance of treatment systems: implications for isotope monitoring in receiving environments.
abstract: Stable nitrogen isotope ratios are routinely used to trace the dispersion and assimilation of wastewater-derived N in receiving environments, but few isotope studies have investigated wastewater treatment plants and ponds themselves. An improved understanding of N isotope compositions in effluent will help assess treatment plant processes and performance and will help trace sources of excess nutrients in receiving environments. Here, we assess N budgets and treatment processes in seven wastewater treatment plants and wastewater stabilisation ponds in northern Australia based on concentrations and isotope ratios of N in effluent. We show that δ15N values in effluent are linked to treatment type, effectiveness of conversion of ammonia and levels of gaseous N emissions. These relationships suggest that N isotope monitoring of wastewater treatment plants and ponds can provide an integrated assessment of treatment performance and gaseous N emissions on a pond- or plant-wide scale that is not readily available through other methods. Our findings further imply that monitoring N isotope ratios in receiving environments cannot be assumed to be universally effective as their sensitivity to uptake of wastewater-derived N will vary with the characteristics of individual treatment systems. Paradoxically, N isotope monitoring is less effective where treatment systems are functioning poorly and where monitoring needs are the greatest.
authors.affiliation: Research Institute for the Environment and Livelihoods, Charles Darwin University, Casuarina, NT, 0810, Australia. niels.munksgaard@cdu.edu.au.
authors.forename: Niels C
authors.initials: NC
authors.lastname: Munksgaard
authors.affiliation: Research Institute for the Environment and Livelihoods, Charles Darwin University, Casuarina, NT, 0810, Australia.
authors.forename: Kanchana N
authors.initials: KN
authors.lastname: Warnakulasooriya
authors.affiliation: Water Services, Power and Water Corporation, Winnellie, NT, 0821, Australia.
authors.forename: Karen
authors.initials: K
authors.lastname: Kennedy
authors.affiliation: Water and Waste, Cairns Regional Council, Cairns, QLD, 4870, Australia.
authors.forename: Lynne
authors.initials: L
authors.lastname: Powell
authors.affiliation: Research Institute for the Environment and Livelihoods, Charles Darwin University, Casuarina, NT, 0810, Australia.
authors.forename: Karen S
authors.initials: KS
authors.lastname: Gibb
mesh_terms: D000641:Ammonia / Q000032:analysis; D001315:Australia; D004777:Environment; D004784:Environmental Monitoring / Q000379:methods; D009584:Nitrogen / Q000032:analysis* / Q000737:chemistry; D009587:Nitrogen Isotopes / Q000032:analysis / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry; D018508:Water Purification / Q000379:methods
chemical_list: D000641:Ammonia; D009584:Nitrogen; D009587:Nitrogen Isotopes; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Ammonia; Gas emissions; Isotopes; Monitoring; Nitrogen; Wastewater