Limiting microbial growth during drinking water distribution is achieved either by maintaining a disinfectant residual or through nutrient limitation without using a disinfectant. The impact of these contrasting approaches on the drinking water microbiome is not systematically understood. We use genome-resolved metagenomics to compare the structure, metabolic traits, and population genomes of drinking water microbiome samples from bulk drinking water across multiple full-scale disinfected and non-disinfected drinking water systems. Microbial communities cluster at the structural- and functional potential-level based on the presence/absence of a disinfectant residual. Disinfectant residual alone explained 17 and 6.5% of the variance in structure and functional potential of the drinking water microbiome, respectively, despite including multiple drinking water systems with variable source waters and source water communities and treatment strategies. The drinking water microbiome is structurally and functionally less diverse and variable across disinfected compared to non-disinfected systems. While bacteria were the most abundant domain, archaea and eukaryota were more abundant in non-disinfected and disinfected systems, respectively. Community-level differences in functional potential were driven by enrichment of genes associated with carbon and nitrogen fixation in non-disinfected systems and γ-aminobutyrate metabolism in disinfected systems likely associated with the recycling of amino acids. Genome-level analyses for a subset of phylogenetically-related microorganisms suggests that disinfection selects for microorganisms capable of using fatty acids, presumably from microbial decay products, via the glyoxylate cycle. Overall, we find that disinfection exhibits systematic selective pressures on the drinking water microbiome and may select for microorganisms able to utilize microbial decay products originating from disinfection-inactivated microorganisms.

In this study, we co-analyze all available 16S rRNA gene sequencing studies from bulk drinking water samples in full-scale drinking water distribution systems.

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This study performed a comprehensive assessment of the impact of Hurricane Maria (HM) on drinking water quality in Puerto Rico (PR) by integrating targeted chemical analysis of both inorganic (18 trace elements) and organic trace pollutants (200 micropollutants) with high-throughput quantitative toxicogenomics and in vitro biomarkers-based toxicity assays. Average concentrations of 14 detected trace elements and 20 organic micropollutants showed elevation after HM. Arsenic, sucralose, perfluorooctanoic acid (PFOA), atrazine-2-hydroxy, benzotriazole, acesulfame, and prometon were at significantly (p < 0.05) higher levels in the post-HM than in the pre-HM samples. Thirteen micropollutants, including four pesticides, were only detected in posthurricane samples. Spatial comparison showed higher pollutant and toxicity levels in the samples from northern PR (where eight Superfund sites are located) than in those from southern PR. Distinctive pathway-specific molecular toxicity fingerprints for water extracts before and after HM and at different locations revealed changes in toxicity nature that likely resulted from the impact of HM on drinking water composition. Correlation analysis and Maximum Cumulative Ratio assessment suggested that metals (i.e., arsenic) and PFOA were the top ranked pollutants that have the potential to cause increased risk after HM, providing a possible direction for future water resource management and epidemiological studies.

18Limiting microbial growth during drinking water distribution is achieved either by maintaining a 19 disinfectant residual or through nutrient limitation without the use of a disinfectant. The impact of 20 these contrasting approaches on the drinking water microbiome is not systematically understood. 21We utilized genome-resolved metagenomics to compare the structure, metabolic traits, and 22 42 in the DWDS to limit microbial growth using high-quality source waters and/or multi-barrier 73 treatment. While some of these drinking water systems may also use chlorine or other chlorine 74 compounds (e.g., chlorine dioxide) at the DWTP, they ensure that chlorine is not detectable prior 75 to distribution. The efficacy of this approach is supported by evidence that incidences of microbial 76 contamination and associated waterborne illnesses are comparable to systems that maintain a 77 disinfectant residual 25, 37 . This suggest that with appropriate source water quality management, 78 treatment, and well maintained infrastructure, drinking water can be safely distributed without 79 disinfectant residuals 25 . 80Despite reports of comparable biological water quality between systems with and without 81 disinfectant residuals, there are a limited number of studies that have systematically compared the 82 microbial community between these two types of systems. Bautista et al (2016) 38 conducted a 83 meta-analyses study involving collation, curation, and comparison of 16S rRNA gene amplicon 84 sequencing data from previously published datasets. While this study was confounded my 85 methodological differences between datasets being used, the key conclusions were that 86 presence/absence of disinfectant residuals impact microbial community structure and membership 87 and that systems without disinfectant residuals are more diverse than their disinfected counterparts. 88Recently, Waak et al (2019) 39 compared biofilms between two drinking water systems, one 89 chloraminated systems and one without a disinfectant residual. Consistent with previous findings 90 they observed higher cell numbers and higher diversity in the system without disinfectant residual, 91 with higher proportional abundance (proportion of total community) of deleterious microbes (i.e., 92 mycobacteria, nitrifiers, corrosion causing bacteria) in the chloraminated system. Both, Bautista 93 et al (2016) 38 and Waak et al (2019) 39 utilized gene-targeted assays (i.e., 16S rRNA gene) to probe 94 drinking water microbiome composition and its differences. While gene-targeted assays can 95 provide valuable information on microbial community structure and membership information, 96

The capacity of microalgae to advance the limit of technology of nutrient recovery and accumulate storage carbon make them promising candidates for wastewater treatment. However, the extent to which these capabilities are influenced by microbial community composition remains poorly understood. To address this knowledge gap, 3 mixed phototrophic communities sourced from distinct latitudes within the continental United States (28°N, Tampa, FL; 36°N , Durham, NC; and 40°N, Urbana, IL) were operated in sequencing batch reactors (8 day solids residence time, SRT) subjected to identical diel light cycles with media addition at the start of the nighttime period. Despite persistent differences in community structure as determined via 18S rRNA (V4 and V8−V9 hypervariable regions) and 16S rRNA (V1−V3) gene amplicon sequencing, reactors achieved similar and stable nutrient recovery after 2 months (8 SRTs) of operation. Intrinsic carbohydrate and lipid storage capacity and maximum specific carbon storage rates differed significantly across communities despite consistent levels of observed carbon storage across reactors. This work supports the assertion that distinct algal communities cultivated under a common selective environment can achieve consistent performance while maintaining independent community structures and intrinsic carbon storage capabilities, providing further motivation for the development of engineered phototrophic processes for wastewater management.