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Measuring nitrification inhibition by metals in wastewater treatment systems: Current state of science and fundamental research needs
Citation:
Li, X., V. Kapoor, C. Impellitteri, AND K. Chandran. Measuring nitrification inhibition by metals in wastewater treatment systems: Current state of science and fundamental research needs. CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY. CRC Press - Taylor & Francis Group, LLC, Boca Raton, FL, 46(3):249-289, (2016).
Impact/Purpose:
Here, we review the physicochemical stressors that can inhibit nitrification and the results obtained with methods that can help us assess inhibition rates. Special attention will be drawn on potential inhibitory effect of metals regulated by EPA’s National Pretreatment Program (USEPA, 2004). We provide a synthesis of studies dealing with nitrification inhibition as they pertain to wastewater and highlight how different inhibitory thresholds have been generated for the same inhibitor. We will argue that some of the variability in the results available in the scientific literature is driven by the different methods used and the physicochemical and biological complexity of wastewater systems. Lastly, we discuss emerging molecular methods that can be used to measure inhibition rates based on gene expression, and the need to improve our understanding of the microbial network implicated in nitrification wastewater systems.
Description:
Wastewater treatment is an important step within the water continuum as it reduces the risks associated with microorganisms as well as organic and inorganic compounds. From a chemical standpoint, treatment effectiveness is linked to carbon and nitrogen removal, although phosphate recovery is also relevant as we move towards sustainable resource recovery. Nitrogen removal is initiated by the conversion of ammonia to nitrate, a process that is carried out by nitrifying microorganisms. Nitrification is considered a key step as it removes the toxic effect of ammonia while the resulting nitrate can be further converted into N2 gas (by autotrophic or heterotrophic bacteria) which is not harmful to the environment. As nitrification is susceptible to a wide range of inhibitory substances, measuring the effect of potential inhibitors on nitrification rates is relevant to maintaining the performance of treatment plants. In this review we discuss the primary methods used to measure nitrification inhibition, their applications, potential limitations, and identify the research gaps that need to be addressed to better achieve nitrification in engineered wastewater treatment systems.
