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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/H2O2 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/H2O2 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/H2O2 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.

One of the two main objectives of this study is to use two pass membrane desalination system and to oxidize permeate of the first pass with ozone, as disinfection by products (DBPs) formed by ozone are rather limited. Second objective of this work; is to increase the pH levels to 10 in the permeate of the first desalination pass in order to promote dissociation of boric acid (B(OH)3) to borate (B(OH)4−). Negatively charged borate can easily be removed by membrane systems because of the charge repulsion. Oxidation efficiency of ozone under pH 10 conditions and the buffer effect of borate were also focused on in this study. Double pass nanofiltration/ reverse osmosis (NF/RO) membrane filtration systems were used for the desalination of model seawater. Permeate of the first membrane filtration was adjusted to pH 10 and oxidized with ozone for 30 mins. Oxidized permeate was then fed to the second membrane filtration in order to investigate boron removal and bromate formation and removal. Boron removal was imp...