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Plastic containers in the range of 5–20 L are widely used – especially in rural African settings – to collect, transport and store water for domestic use, including drinking, bathing and hygiene. The pathogen content of the waters in these containers has not been adequately characterized as yet. This paper presents the primary findings of a synoptic survey of drinking water quality samples from these containers and involved collection of bacterial indicator and pathogenicity gene data. In total, 571 samples of a variety of waters were taken in rural communities in South Africa and the Escherichia coli numbers measured. Of the E. coli positive samples, 46% (n = 148) were screened for the presence of E. coli pathogen gene markers. Though synoptic, the survey provided many insights into the issues that drove the study. Container use markedly degraded water quality as judged by indicator counts, even where improved water supply services were in place. Household container use also appeared to promote regrowth or contamination of containers with pathogenic E. coli strains. Polymerase chain reaction (PCR) analysis also showed that the diversity of potential pathogenic E. coli carrying virulence genes was great. All seven genes screened for (Ial, Stx1, Stx2, EaeA, Eagg, ST, LT) were found in the waters, alone or as mixtures (number of different combinations = 31) including those characteristic of the more dangerous invasive and haemorrhagic E. coli strains. Given the central role of containers in the management of water supply to rural communities, it is clear the microbiology of these waters requires much further characterization.

Waterborne disease outbreaks have been associated with periods of heightened source water pathogen concentrations in treated drinking-water supplies. For their management it is necessary to identify and quantify the impacts of events which lead to adverse concentration fluctuations. The aim of this work was to estimate relative microbial risks to water consumers arising from one such event: rainfall-induced runoff entering a surface drinking-water reservoir in an Australian agricultural catchment. Runoff events are known to influence both the source water entering a reservoir and the ability of a reservoir to act as a barrier to pathogen progression. Hydrograph separation methods were used to distinguish ‘runoff event’ from baseflow periods and pathogen concentrations of the inflow to the reservoir during runoff and baseflow periods respectively were estimated. Relative impacts of runoff event periods on health risks to consumers were assessed using Quantitative Microbial Risk Assessment principles. Runoff event conditions predominated 14 % of the time. The proportions of infections attributable to runoff event periods from Cryptosporidium , Giardia and Campylobacter spp. were 57 %, 80 %, and 28 % respectively. Daily infection risks were greatest in winter months than other seasons primarily due to the higher frequency of runoff events. Results from this and similar analyses, aiming to assess impacts of explicitly identified events on consumer health risks, provides important information for water system risk management, e.g. identifying periods of heightened risk and setting management priorities.

The objective of this study was to assess the use of on-line monitoring to support the QMRA at water treatment plants studied in the EU MicroRisk project. SCADA data were obtained from three Catchment-to-Tap Systems (CTS) along with system descriptions, diary records, grab sample data and deviation reports. Particular attention was paid to estimating hazardous event frequency, duration and magnitude. Using Shewart and CUSUM we identified ‘change-points’ corresponding to events of between 10 min and > 1 month duration in timeseries data. Our analysis confirmed it is possible to quantify hazardous event durations from turbidity, chlorine residual and pH records and distinguish them from non-hazardous variability in the timeseries dataset. The durations of most ‘events’ were short-term (0.5–2.3 h). These data were combined with QMRA to estimate pathogen infection risk arising from such events as chlorination failure. While analysis of SCADA data alone could identify events provisionally, its interpretation was severely constrained in the absence of diary records and other system information. SCADA data analysis should only complement traditional water sampling, rather than replace it. More work on on-line data management, quality control and interpretation is needed before it can be used routinely for event characterization.

In this paper the results of a sampling programme, undertaken as part of the EU MicroRisk project, are described. This project was undertaken to ascertain the occurrence of pathogens and indicators in the River Thames and their subsequent removal through a treatment works. Appropriate physico-chemical surrogates, as determined by statistical correlation are proposed for the microorganisms identified in the raw water. This study shows that under normal raw water conditions the treatment works is able to remove microbial contamination with a significant margin of safety.

The ‘H2S test’ is being advanced for microbiological water quality testing where conventional coliform based methods are impractical or too expensive. It involves ambient temperature incubation of water samples with nutrient formulated to generate hydrogen sulphide when ‘faecal’ bacteria are present. Recently a WHO review identified several concerns including the limited number of comparative studies, formulation variability, and false positives and negatives. In response we have compared the H2S test's ability to detect and quantify faecal contamination in an aquifer impacted by septic tank leachfields with measurements obtained concurrently using conventional bacterial indicators, coliphages, faecal sterol biomarkers, Cryptosporidium and Giardia. Like these other analytes, H2S testing detected a contamination gradient ranging from high (septic liquid) to moderate (exfiltration zones), to background (e.g. domestic bores), corresponding to indicator removal + dilution by factors >106. Presence/absence tests could not distinguish between heavily and slightly contaminated waters, whereas multi-tube testing (e.g. 10 × 10 mL arrays) did. It was concluded that while the WHO review concerns are justified, the H2S test performance shows promise in sanitary survey work, can be improved by employing an mpn approach and has potential to aid in the protection of source water and identifying contaminated groundwater.

The quality of effluent from an on-site sewage treatment system is a critical factor in designing the disposal area and, hence, ensuring the sustained performance of the system. Contaminant concentrations in effluent are typically specified in regulatory guidelines or standards; however, the accuracy of these guideline values are brought into question due to the poor performance of septic tanks and the high failure rates of disposal systems reported here and elsewhere. Results from studies of septic tank effluent quality indicated that the effluent is of poorer quality than currently suggested by guidelines. Aerated wastewater treatment systems were found to perform to accreditation guidelines; however, insufficient nutrient data is presently available to assess nutrient loads. It is proposed that the 80th percentile of system performance be adopted as the design value for sizing effluent disposal areas to minimise failure associated with overloading. For septic tanks this equates to 660 mg L−1 SS, 330 mg L−1 BOD, 250 mg L−1 TN and 36 mg L−1 TP.

Data collected from centralised and decentralised sewage treatment plants throughout Sydney9s drinking water catchments was used to calculate the relative catchment loads of Cryptosporidium , enteric viruses, nitrogen and phosphorus for an initial screening assessment. Loads were assessed at median and 90 percentile values for expected and worst-cases scenarios. The expected scenario in the Sydney drinking water catchments is that decentralised systems (servicing 32,800 people) provide similar total loads to centralised systems (serving 70% of the catchment population) for total phosphorus (37,090 kg.y -1 ), Cryptosporidium (10 11 oocysts.y -1 ) and enteric viruses (9.1 × 10 13 y -1 ), but higher loads of total nitrogen (237,610 vs. 136,740 kg.y -1 ). Decentralised systems, however, were predicted to have higher loads in the worst-case scenario with 620,620 kg.y -1 TN, 82,040 kg.y -1 TP, 7.3 × 10 13 Cryptosporidium oocysts.y -1 and 9 × 10 15 enteric viruses per year. Greater load variability was experienced with decentralised systems, which presumably reflects less reliability in their current operation and maintenance. Overall, catchment water quality is therefore not only affected by sewage disposal methods, but also failure issues. Decentralised system disposal to land may afford a degree of mitigation that can be enhanced, if the degree of failure is reduced.

The supply of unfiltered disinfected drinking water from Melbourne's fully protected catchments means that the water-quality managers must ensure that the source water poses no public health risk. High turbidity is currently used as a surrogate of pathogens, and harvesting of water is based on its measurement. The work presented here summarises suspended particle and associated pathogen, microbial indicator and faecal biomarker concentrations collected to (a) quantify turbidity in an Australian water supply system and (b) assess the possibility of increasing water harvesting from selected tributaries. Pathogens and microbial indicators were present in low numbers in these source waters; increased turbidity during storm events was not associated with an increase in pathogen concentration. The results confirmed that protected catchments, along with good management, were effective barriers to pathogen contamination. Aesthetic issues still need to be addressed, but no measurable increase in microbiological risk was associated with storm-generated particles.

Pathogens and nutrients released from on-site sewage systems represent a risk to surface and ground water quality, particularly where there are sensitive receiving waters such as in drinking water catchments. Buffer zones between on-site systems and waterways are one barrier used to protect water quality. The increased time and distance they provide increases the opportunities for the effluent purification functions of the soil to occur. A risk management model is proposed to assess the efficacy of the buffer zones in Sydney's drinking water catchments. The model is the basis for the development of performance based setback distances for on-site systems from waterways, and incorporates stochastic analysis of pathogen and nutrient transport in the environment and consideration of the effluent quality variability from on-site systems. Catchment-scale integration of contaminant transport is employed to facilitate a risk assessment of on-site systems. The risk management model also allows for the impact of on-site system management and maintenance on catchment water quality to be assessed through scenario building and feedback mechanisms.

Reliance on coliform monitoring of ground waters is slowly changing as is reflected in the proposed US EPA Ground Water Rule. In line with this we have investigated the use of an expanded range of faecal indicators and potential surrogate analytes within the Gwelup and Jandakot borefields in Perth, Western Australia. The aims of the study included comparing contamination in bores and surface waters in vulnerable locations, quantifying aquifer removal of microorganisms, trialing novel biochemical pollution indicators such as faecal sterols, assessing Escherichia coli as a measure of groundwater contamination and generating data for risk assessments. Sampling was undertaken of nine production bores, nine monitoring bores and four surface waters for 32 parameters comprising seven microbial indicators, 12 physico-chemical parameters and 13 biomarkers (including 8 faecal sterols and caffeine) at sampling stations potentially impacted by urban development. Concentrations of microbial indicators and biomarkers followed the pattern: basins >> monitoring bores >> production bores. Only one production bore sample contained bacterial indicators (0.1 enterococci.100 mL-1 on 1 occasion). Of the faecal biomarkers, coprostanol was generally at background levels. Cholesterol appeared to be a more sensitive measure of infiltration, but was also effectively removed. E. coli appeared to be a less sensitive indicator than enterococci. None of the physico-chemical parameters were useful surrogates. Overall apparent faecal microbial removal by aquifer filtration averaged >4-5 logs (not accounting for viruses). To maximise warning time and assay sensitivity it is suggested that enterococci be considered as the key bacterial indicator rather than E. coli and that different combinations of indicators and biomarkers be used to identify aquifer locations at risk, the presence of significant faecal material, and the likely presence of pathogens.