The results provide insight into microbial pathogen detection that may aid in the monitoring of microbial water quality within DWDS prior to customer exposures.

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Using local sources (roof runoff, stormwater, graywater, and onsite wastewater) to meet non-potable water demands can minimize potable water use in buildings and increase supply reliability. In 2017, an Independent Advisory Panel developed a risk-based framework to identify pathogen log reduction targets (LRTs) for onsite non-potable water systems (ONWSs). Subsequently, California's legislature mandated the development and adoption of regulations—including risk-based LRTs—for use in multifamily residential, commercial, and mixed-use buildings. A California Expert Panel was convened in 2021 to (1) update the LRT requirements using new, quantitative pathogen data and (2) propose treatment trains capable of meeting the updated LRTs. This paper presents the updated risk-based LRTs for multiple pathogens (viruses, protozoa, and bacteria) and an expanded set of end-uses including toilet flushing, clothes washing, irrigation, dust and fire suppression, car washing, and decorative fountains. The updated 95th percentile LRTs required for each source water, pathogen, and end-use were typically within 1-log10 of the 2017 LRTs regardless of the approach used to estimate pathogen concentrations. LRT requirements decreased with influent pathogen concentrations from wastewater to graywater to stormwater to roof runoff. Cost and footprint estimates provide details on the capital, operations and maintenance, and siting requirements for ONWS implementation.

Water treatment professionals are generally aware of the issues regarding the fate and transport of pathogens within watersheds. However, not all water treatment professionals are in a scientific field nor do they all have the same level of knowledge of the range of international projects being conducted to address this issue. To counter a current lack of quantitative data on the biophysical and chemical parameters that drive pathogen survival and transport in watersheds, the authors created a conceptual model of a watershed that water suppliers can use as a starting point to create their own pathogen risk assessment and to prioritize their research to target identified knowledge gaps. These findings make it possible to identify the next steps for research and focus on the chemical, physical, and biological processes that underpin pathogen transport and attenuation while avoiding duplicative research efforts.

Optimisation of nutrient removal processes requires a detailed understanding of the microbial physiologies actually occurring within the biomass of different treatment zones, and also knowledge of how these communities respond to environmental factors. This paper describes a suite of four independent and complementary, microbiological techniques, utilised to obtain detailed assessments of wastewater bacterial biomass. Examples of these techniques are shown as applied to biofilms from two surface-flow wetlands used for treating sewage effluent. Intact biofilms were prepared via freezing, followed by cryosectioning and direct microscopic observation. This approach was combined with prior, in situ incubation of biofilm with radiolabelled thymidine to assess in situ bacterial growth rates. Individual bacterial cells were assessed microscopically for in situ respiratory activity and phylogenetic identity, respectively through use of an inducibly-fluorescent redox stain (CTC), and fluorescent in situ hybridisation (FISH) of ribosomal RNA (rRNA). These complementary techniques enabled assessment of individual biofilm clusters according to their in situ status (growth, respiration, spatial location and phylogenetic affiliation). This approach detected significant spatial variations in biofilm; limited the bias inherent in data obtained using any one technique, and provided greater detail of subpopulations within the microbial community.

Two prospective studies on the occurrence of human viruses in samples of coastal & river origin have been undertaken since September 1989. Viruses were detected using concentration methods & cell culture techniques. Water samples (100L) were reduced to 1L using hollow fibre ultrafiltration and then treated with PEG. Sewage and sediment samples were treated with PEG only. Over a two year period, viruses were detected in 24/202 (12%) of water samples and 29/60 effluents from the river system. Coastal waters have been contaminated by cliff edge discharge of sewage for at least the last 70 years. Recently, deepwater ocean outfalls have been installed to discharge effluent some 3 km away from the coast. Prior to the installation of deepwater ocean outfalls viruses were detected in 28% of water samples compared to 9% post installation. In sediment samples viruses were isolated in 87/260 (34%) samples, the discharge via the new outfalls having no effect on the isolation rate. The data points to long term survival of viruses sediments and/or contamination from other sources such as storm water discharge: 10-25% of storm water drains were also found to be positive for viruses. The viruses isolated were enteroviruses, adenoviruses & reoviruses. Although viruses were consistently isolated with some seasonal trends, comparisons between the detection of viruses in clinical and environmental samples over this two year period were inconclusive.