Characteristics of the formation and toxicity index of nine newly identified brominated disinfection byproducts during wastewater ozonation

Antibiotics removal and antimicrobial resistance control by ozone/peroxymonosulfate-biological activated carbon: A novel treatment process

Biological activated carbon (BAC) is one of the important treatment processes in wastewater and advanced water treatment. However, the BAC process has been reported to have antimicrobial resistance (AMR) risks. In this study, a new BAC-related treatment process was developed to reduce AMR caused by BAC treatment: ozone/peroxymonosulfate-BAC (O3/PMS-BAC). The O3/PMS-BAC showed better treatment performance on the targeted five antibiotics and dissolved organic matter removal than O3-BAC and BAC treatments. The O3/PMS-BAC process had better control over the AMR than the O3-BAC and BAC processes. Specifically, the amount of targeted antibiotic-resistant bacteria in the effluent and biofilm of O3/PMS-BAC was only 0.01-0.03 and 0.11-0.26 times that of the BAC process, respectively. Additionally, the O3/PMS-BAC process removed 1.76 %-62.83 % and 38.14 %-99.27 % more of the targeted ARGs in the effluent and biofilm than the BAC process. The total relative abundance of the targeted 12 ARGs in the O3/PMS-BAC effluent was decreased by 86 % compared to the effluent after BAC treatment. In addition, Proteobacteria and Bacteroidetes were probably the main hosts for transmitting ARGs in this study, and their relative abundance decreased by 9.6 % and 6.0 % in the effluent of the O3/PMS-BAC treatment compared to that in BAC treatment. The relationship analysis revealed that controlling antibiotic discharge was crucial for managing AMR, as antibiotics were closely related to both ARGs and bacteria associated with their emergence. The results showed that the newly developed treatment process could reduce AMR caused by BAC treatment while ensuring effluent quality. Therefore, O3/PMS-BAC is a promising alternative to BAC treatment for future applications.

Microbial bromate reduction following ozonation of bromide-rich wastewater in coastal areas

Ozonation of wastewater can reduce the release of organic micropollutants, but may result in the formation of undesirable by-products, such as bromate from bromide. Bromide is one of the most abundant ions in seawater, the primary precursor of bromate during ozonation, and the end product in microbial bromate reduction. Investigations were carried out to compare the concentration of bromide in wastewater in coastal and non-coastal catchment areas, to monitor bromate formation during ozonation, and to assess the potential for subsequent bromate reduction with denitrifying carriers. Higher bromide concentrations were systematically observed in wastewater from coastal catchment areas (0.2-2 mg Br^-/L) than in wastewater from non-coastal areas (0.06-0.2 mg Br^-/L), resulting in elevated formation of bromate during ozonation. Subsequent investigations of bromate reduction in contact with denitrifying carriers from two full-scale moving bed biofilm reactors (MBBRs) showed that 80 % of the bromate formed during ozonation could be reduced to bromide in 60 min with first-order rate constants of 0.3-0.8 L/(g_biomass·h). Flow-through experiments with denitrifying carriers also showed that combined reduction of bromate and nitrate could be achieved below a concentration of 2 mg NO_x^--N/L. These findings indicate that bromide-rich wastewater is more likely to be of concern when using ozonation in coastal than in non-coastal areas, and that bromate and nitrate reduction can be combined in a single biofilm reactor.