Enrichment of 15N/14N in wastewater-derived effluent varies with operational performance of treatment systems: implications for isotope monitoring in receiving environments

Niels C. Munksgaard, Kanchana N. Warnakulasooriya, Karen Kennedy, Lynne Powell, Karen S. Gibb

    Research output: Contribution to journalArticle

    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.

    Original languageEnglish
    Article number36
    Pages (from-to)1-10
    Number of pages10
    JournalEnvironmental Monitoring and Assessment
    Volume189
    DOIs
    Publication statusPublished - Jan 2017

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