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Developing Biological Surrogates for Monitoring Treatment Performance of Onsite Non-Potable Water Systems
Citation:
Brinkman, N. Developing Biological Surrogates for Monitoring Treatment Performance of Onsite Non-Potable Water Systems. 2019 UNC Water Microbiology Conference, Chapel Hill, North Carolina, May 13 - 16, 2019.
Impact/Purpose:
This presentation describes SSWR research results for efforts to safely implement onsite non-potable water reuse systems.
Description:
Decentralized, non-potable water reuse can provide economic and environmental benefits to water-stressed communities. However, wide-spread implementation of onsite non-potable water systems (ONWS) has been hindered by a lack of effective monitoring strategies to ensure treatment performance meets risk-based pathogen reduction requirements to protect public health. Pathogen densities can be highly variable in ONWS owing to intermittent infections among the small contributing population and, therefore, cannot be used to verify that risk-based treatment requirements are met. Similarly, traditional fecal indicator bacteria (FIB) occur at low and variable levels, prohibiting FIB from use as a treatment performance surrogate. As an alternative, non-pathogenic microorganisms present in the source water could serve as surrogates to monitor pathogen removal, provided they consistently occur at concentrations high enough to observe the log reduction target (LRT) of the reference pathogen and are removed at similar rates as reference pathogens. Using high-throughput sequencing, bacteria commonly reported from human skin were identified in freshly collected graywater and subsequent quantitative analysis confirmed their occurrence at levels above the LRT threshold for enteric bacteria. However, the relative abundances of human skin bacteria declined within the ONWS and were replaced by bacteria growing in the pipe network. These ONWS resident bacteria could be potential surrogates for monitoring removal of enteric bacterial pathogens. Additionally, we quantified several candidate virus surrogates (pepper mild mottle virus, crAssphage, myoviruses and gokushoviruses) along with norovirus in the source water of 3 ONWS using droplet digital PCR. Concentrations of pepper mild mottle virus and crAssphage were greatest in the blackwater ONWS, while myoviruses were the greatest in the graywater ONWS. The viral surrogate concentrations are sufficient to confirm LRT for enteric viruses. In this presentation, we will highlight our research efforts to identify microbial surrogates to monitor pathogen removal in ONWS utilizing various water sources and multiple end uses.
