Intermittent piped water supply (IWS) is a distribution network that only supplies water for limited durations. Intrusion is a common mechanism for pathogen entry into IWS networks due to cross connections, backflows, and low pressures. Bacteria such as Escherichia coli (E. coli) can be incorporated into the bulk drinking water and biofilms of the pipes and can cause illness. Little is known, however, about the persistence of pathogen indicators, such as E. coli in IWS, which is characterized by common intrusion events, inconsistent disinfectant residuals, and regular stagnation. This study examined the persistence of E. coli in parallel pilot scale drinking water supply loops, with one loop operating as an IWS and the other as a continuous water supply, both supplied by chloraminated drinking water. Between 2-log and 4-log removal of E. coli was found immediately upon its entry to the pilot distribution systems, but took 10 minutes to 1 hour to reach non-detect levels, despite whether the intrusion event occurred before or after the IWS was restarted. Knowing the time to complete removal of E. coli provides insight into how to best manage and treat IWS and mitigate associated health risks. Our experimental set-up had large variability in disinfectant residuals, likely impacting results. We did not find any incorporation of E. coli into the biofilms of the piped systems during the experimental time frame. Future experiments will examine persistence of E. coli in water without chlorine residual and impacts on E. coli incorporation into biofilms over longer time periods.

Undesirable microbes in drinking water distribution systems (DWDSs) may lead to deterioration of water quality, and spreading the waterborne diseases. Four DWDSs with different disinfectants including free chlorine, chloramine and chlorine dioxide were investigated in this study. Chloramine had a more profound impact on DWDS microbial communities than the other two disinfectants. For example, chloramination DWDS enriched more Mycobacterium and Nitrospira, and harbored highly similar eukaryotic communities across different sampling sites.

Diverse eukaryotic communities were observed in DWDSs, with Nematozoa, Ascomycota, and Gracilipodida as the most dominant phyla. Compared to the bacterial community, the eukaryotic community in the four DWDSs varied to a lesser degree among the four DWDSs. The null modelling approach revealed that stochastic processes were more important than deterministic events in determining the eukaryotic communities even in the presence of disinfectant residuals. That illustrated the limited effect of the disinfectant on the eukaryotic community.

Eight free-living amoebae (FLA) including Vermamoeba, Flamella, Nuclearia, Physarum, Chrysamoeba, Naegleria, Dictyostelium and Ceratiomyxella were found in the four DWDSs. Less FLA were observed in chlorine dioxide DWDS, illustrating that chlorine dioxide may be more effective to control FLA. The identified eight amoebae genera were associated with 45 eukaryotic and 121 bacterial genera including Mycobacterium and Legionella. The amoebal community was not affected by the disinfectant concentration, and the key factors affecting the amoebal community were nitrate, ammonia, turbidity and conductivity.

Overall, the results of this study will provide insights to factors affecting microbial characteristics in DWDSs with different disinfectant types.

Lead contamination in drinking water (DW) supplies is a major concern as millions of lead service lines remain in use in the USA. While corrosion control methods, such as the addition of orthophosphate (PO₄^3-) are important in protecting the public from lead, PO₄^3- introduction may cause increased microbial growth due to the increase in biologically available phosphorus. This is an important consideration given that many DW systems are phosphorus limited and a natural habitat for nontuberculous mycobacteria (NTM), an example of drinking water-associated pathogens that can cause infections in immunocompromised individuals (DWPIs).

The impact of PO₄^3- corrosion control on DWPI abundance was assessed in a full-scale DW distribution system (DS) in Pittsburgh, PA. Water samples were collected throughout the DS before and after PO₄^3- corrosion inhibitor addition at seven locations representing various residence times. Using ddPCR, a significant 2-log increase in the absolute abundance of NTM was detected 7 months after PO₄^3- addition. To elicit the impact of PO₄^3- on NTM, further experimentation on NTM growth and aggregation (biofilm formation) potential in the presence and absence of PO₄^3- was conducted. No significant impacts on NTM growth were observed after PO₄^3- addition, however, PO₄^3- addition did significantly impact aggregation potential suggesting increasing PO₄^3- presence interferes with NTM biofilm formation and detachment processes. Overall, the findings of this study provide insights into the impacts of PO₄^3- addition on DW microbial communities in a full-scale DS and aims to help inform water utilities about the potential unexpected impacts of full-scale PO₄^3- addition.

The COVID-19 pandemic illustrates the importance of understanding the behavior and control of human pathogenic viruses in the environment. Exposure via water (drinking, bathing, and recreation) is a known route of transmission of viruses to humans, but the literature is relatively void of studies on the persistence of most viruses, especially coronaviruses, in water and their susceptibility to chlorine disinfection. To fill that knowledge gap, we evaluated the persistence and free chlorine disinfection of human coronavirus OC43 (HCoV) and its surrogates, MHV and porcine transmissible gastroenteritis virus (TGEV), in drinking water and laboratory buffer using cell culture methods. Human coronavirus and its surrogates remained infectious in drinking water and phosphate buffer at room temperature for days to weeks, though their decay rates varied between viruses in different water matrices. In drinking water, MHV showed the highest decay rate of 2.15 d^-1 which was followed by HCoV OC43 (0.97 d^-1) and TGEV (0.59 d^-1); while in phosphate buffer, HCoV OC43 (0.70 d^-1) decayed faster than MHV (0.38 d^-1) and TGEV (0.23 d^-1). Upon free chlorine disinfection, the inactivation rates of coronaviruses were independent of free chlorine concentration and no longer impacted by water matrices, though they still varied between viruses. Our results will be of immediate use to inform water policies for pandemic response and also highlight the cruciality of selecting appropriate virus surrogates and water matrices in research related with human pathogenic virus persistence and disinfection in water.

The Safe water drinking act (SDWA) ensures water quality regulations are enforced in municipal water systems, meaning individuals obtaining drinking water (DW) from private wells are often not protected by legislation. Furthermore, as well water is the source for many rural and low-income minority communities, there is a need to assess whether well water poses a human health concern. In addition, the SDWA does not currently monitor many emerging chemical and microbial contaminants, such as Drinking Water Associated Pathogens of the Immunocompromised (DWPI) (e.g., Legionella pneumophila, nontuberculous mycobacteria) which can cause infections in our vulnerable members of society. Given this, it is essential we understand if DW obtained from wells contains higher DWPI concentrations that municipally treated DW.

This research aimed to compare the presence of chemical contaminants and DWPIs in 20 wells and 20 municipal sources. DW samples collected from homes in rural Iowa were processed for 32 chemical contaminants using standard methods, DWPI abundance using dd PCR assays and microbial community assessment using 16S rRNA amplicon sequencing. Results indicate that residents using well water are, on average, exposed to more chemical and microbial contaminates than those receiving DW from a municipal supply. At the microbial community level, municipal and well water sources contain distinct microbiomes, with well sources containing two times higher species richness. Overall, this pilot study helped to increase our understanding of the largely unknown potential exposures (chemical and biological) posed by well DW and provide clear and tangible information which can help inform vulnerable communities.