Risk assessment is critical for identifying target concentrations of antibiotic resistant pathogens necessary for mitigating potential harmful exposures associated with water reuse. However, there is currently limited available data characterizing the concentrations of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in recycled water to support robust efforts at risk assessment. The objective of this systematic review was to identify and synthesize the existing literature documenting the presence and abundance of ARB and ARGs in recycled water. In addition, this review identifies best practices and explores monitoring targets for studying ARB and ARGs in recycled water to guide future work and identifies key research needs aimed at better supporting quantitative microbial risk assessment focused on recycled water and antibiotic resistance. Future efforts to collect data about ARB and ARG prevalence in recycled water should report concentration data per unit volume. Sample metadata should also be provided, including a description of treatment approach, a description of planned water uses (e.g., potable, irrigation), methods for conveyance to the point of use, and available physicochemical water quality data. Additional research is needed aimed at identifying recommended ARB and ARG monitoring targets and for developing approaches to incorporate metagenomic data into risk assessment.

This study focuses on developing and demonstrating feasibility of an integrated chemical precipitation and membrane filtration method for recovering phosphorus (P) and ammonia (NH 3 -N) in two separate streams from anaerobic digestate generated from municipal wastewater. Nutrient recovery from waste streams creates alternative raw material sources of fertilizers and offers opportunities for reduced energy usage and CO 2 emissions compared with their conventional production processes.Using both synthetic and real anaerobic digestates, the effects of ferrous dosage and precipitation pH on P recovery through vivianite precipitation was examined. Fe/P molar ratio 2.1 at circumneutral pH was found as an optimal condition for ~100% P recovery. The P-free digestate was further treated with polyelectrolyte-modified nanofiltration (NF) membranes to separate NH 3 -N and the organic constituents as a means of N recovery. The surface-modified membranes demonstrated ~2X NH 3 -N/ organic carbon selectivity versus commercial NF membranes. This integrated Fe-enabled chemical precipitation and membrane-based process demonstrates a unique approach to sustainably recover critical nutrients from wastewater.

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