Effect of advanced oxidation on N-nitrosodimethylamine (NDMA) formation and microbial ecology during pilot-scale biological activated carbon filtration

Abstract

Water treatment combining advanced oxidative processes with subsequent exposure to biological activated carbon (BAC) holds promise for the attenuation of recalcitrant pollutants. Here we contrast oxidation and subsequent biofiltration of treated wastewater effluent employing either ozone or UV/HO followed by BAC during pilot-scale implementation. Both treatment trains largely met target water quality goals by facilitating the removal of a suite of trace organics and bulk water parameters. N-nitrosodimethylamine (NDMA) formation was observed in ozone fed BAC columns during biofiltration and to a lesser extent in UV/HO fed columns and was most pronounced at 20 min of empty bed contact time (EBCT) when compared to shorter EBCTs evaluated. While microbial populations were highly similar in the upper reaches, deeper samples revealed a divergence within and between BAC filtration systems where EBCT was identified to be a significant environmental predictor for shifts in microbial populations. The abundance of Nitrospira in the top samples of both columns provides an explanation for the oxidation of nitrite and corresponding increases in nitrate concentrations during BAC transit and support interplay between nitrogen cycling with nitrosamine formation. The results of this study demonstrate that pretreatments using ozone versus UV/HO impart modest differences to the overall BAC microbial population structural and functional attributes, and further highlight the need to evaluate NDMA formation prior to full-scale implementation of BAC in potable reuse applications.

Persistent contaminants of emerging concern in ozone‐biofiltration systems: Analysis from multiple studies

“…While other studies reported moderate susceptibility of sucralose to increasing ozone dose (Sundaram et al, 2020;Vatankhah et al, 2019), only minor sensitivity was observed ( Figure 2). The removal of NDMA was also limited by ozonation due to its low k O 3 (0.052 M −1 s −1 ) and low susceptibility to hydroxyl radical oxidation (k OH = 4.5 × 10 8 M −1 s −1 ), as also reported by others (Bacaro et al, 2019;Hollender et al, 2009;D. Li et al, 2017;Sundaram et al, 2020).…”

“…Organic macromolecules with highly susceptible sites for ozone oxidation, such as aromatic and amino acids functional groups, can react to form oxidation byproducts such as aldehydes, ketones, and carboxylic acids (Legube, 2003), as well as nitrosamines such as NDMA and NMOR (Bacaro et al, 2019; Bourgin et al, 2018; D. Li et al, 2017). As expected, the presence of NDMA and NMOR in ozonated effluents was also observed in a number of studies reviewed as depicted in Figure 5a and b.…”

A performance‐based indicator chemical framework for potable reuse

“…NDMA has good removal in biofiltration (Bacaro et al, 2019), so it may be removed to DR below four prior to UV photolysis in the above scenario. However, if the ozonation NDMA precursors are relatively high at the site, detectable NDMA could pass through the biofiltration (Li et al, 2017). In such a case, NDMA would be a key health‐based indicator targeted by UV and could potentially qualify as a PBI.…”

Occurrence and Fate of Ultramicrobacteria in a Full-Scale Drinking Water Treatment Plant

“…Consequently, with biomass accumulation and shear forces exerted by hydraulic shocks, biofilms would detach from and pass through the BAC filter media, thus increasing cell density in the BAC effluent (Boon et al, 2011; Besmer and Hammes, 2016). Nevertheless, a diverse microbial biofilm community that colonizes in BAC can contribute to improving water treatment efficiency through the metabolism of nutrients and organics (Li D. et al, 2017).…”