Water Journal : Water Journal July 2012
public health refereed paper technical features 82 JULY 2012 water average human faecal contamination. From most contaminated to least (based on average % human contamination), these were Site 7 (45%), Site 9 (38%), Site 2 (25%), Site 5 (23%), Site 13 (13%), Site 18 (12%), Site 10 (12%), Site 6 (8%), Site 16 (8%), Site 8 (3%) Site 14 (3%), Site 17 (2%), Site 1 (1%), Site 3 (1%) and Site 11 (1%) (Figure 4). There were four single events which were estimated to have either equal or higher human contamination than the maximum average percentage human contamination (45%). The highest single event for human contamination (97%) was estimated for the 19 April 2000 water sample collected from Site 9. Two more events were estimated for 19 April 2000 water samples, which were collected from Site 2 (88%) and Site 7 (45%). The remaining single event was estimated for the 9 March 2001 water sample collected from Site 9 (55%). Corresponding coprostanol concentrations and coprostanol/5α-cholestanol ratios for these single four events were 5227ng/L and 3.7; 6864ng/L and 8.3; 327ng/L and 1.1; and 816ng/L and 1.9, respectively. Site 2 and Site 18 fulfilled criteria #1 and #2 and were in the ambiguous region for criteria #3. Since the average concentrations of coprostanol were above 200ng/L, these sites were estimated as contaminated by human faecal matter. Site 1 (1%) and Site 18 (12%) were estimated to have minimal average human faecal contamination, but with comparatively high ratios of coprostanol/5α-cholestanol (0.52 and 0.72 respectively) and absolute concentrations of coprostanol (81ng/L and 227ng/L respectively), this was considered an underestimate. Site 10 satisfied all but one criterion for human faecal contamination and that criterion was a borderline case. With an average concentration of 763ng/L of coprostanol, this site was considered certainly tainted by human faecal contamination. The significantly higher cholesterol concentration, that affected criterion #3, suggested bird faeces may have been responsible for a lot of the thermotolerant coliforms in the samples, thereby dampening the human component. One of the samples collected from Site 1 fulfilled all the "contamination" criteria, but with a modest value of 0.6 for the coprostanol/5α-cholestanol ration and 56ng/L of coprostanol, the estimate of 3% human faecal contamination out of approximately 2000cfu/100mL thermotolerant coliforms and enterococci was considered right. This sample also had the lowest thermotolerant coliform/ Clostridium perfringens ratio. Further considering site-specific information available at the time of the investigation, this site was also considered to be impacted by dog faeces. Site 4, Site 12 and Site 15 showed relatively low average coprostanol concentrations (ranging from 0ng/L to 65ng/L) and coprostanol/5α-cholestanol ratios (ranging from 0.12 to 0.38). Given the low absolute concentrations and the low coprostanol/cholesterol ratios, these sites were estimated as not impacted by human faecal contamination. Site 19 was a far more borderline case, with most criteria falling into the borderline category. With 561ng/L of coprostanol in one sample, it could be suggested that a human component was present. The remaining four samples did not fulfil the criteria and also had very low concentrations of coprostanol (< 10ng/L). The outcomes of this study, along with Hunter Water's other water quality and environmental studies, assisted in determining key remediation targets for each sub-catchment across the study area in terms of gross pollutants, nutrients, toxins and human pathogens (CH2M HILL, 2001). In relation to sewer overflows in wet weather, the UMP recommended that variable stormwater containment objectives across the Newcastle catchment would provide the best overall outcome for the catchment. Based on a cost-benefit analysis, the program was optimised to provide the highest level of improvement in the sub-catchments with the highest environmental and social sensitivities (CH2M HILL, 2000b). The UMP was reviewed and endorsed by the NSW EPA in 2002 and Hunter Water has since been progressively implementing the UMP's recommendations. Works completed to date include sewer relining across the catchment to reduce groundwater infiltrating into the sewer system and identification of illegal stormwater connections. In addition, a series of new wet weather pumping stations is being constructed to augment the capacity of the existing system and transfer excess flows away from known overflow areas. The outcome of this work is a reduction in stormwater flows entering the sewer system in the first place, and an overall reduction in sewer overflows and, hence, improved receiving water quality for human recreational activities. Conclusions Faecal sterol profiles were obtained from water samples collected from a total of 19 sites located within the Newcastle catchment from five wet weather sampling events during March 2000 and February 2002. An assessment of the various faecal indicator bacteria generally showed events of high loading, which rendered the water quality unsuitable at several of the sites for primary contact such as swimming or bathing according to ANZECC (2000) guidelines. Based on average faecal sterol profiles obtained from the water samples collected during five sampling events, faecal sterol ratios generally estimated diffuse sources such as birds as the most significant contributing source (ranging from 15% to 100%) of the total detected faecal pollution. A total of 15 sites were estimated to be impacted by human faecal contamination, with the maximum average human contamination level at any of these sites being 45% of the total detected faecal pollution. Out of these 15 sites, only one site was estimated with > 40%, three sites between 20--40% and 10--20% each and eight sites with < 10% average human faecal contamination. Presence of average herbivore contamination was estimated as minimal for all the sites except for Site 14 (74%) and Site 7 (40%), which were estimated to have significant herbivore contamination. The outcomes of this study, along with Hunter Water's other water quality and environmental studies, were then fed into the UMP, which was reviewed and endorsed by the NSW EPA in 2002. Hunter Water has since been progressively implementing the UMP's recommendations, which has resulted in identifying higher risk catchment areas and key remediation targets in terms of gross pollutants, nutrients, toxins and human pathogens. This further resulted in implementing upgrade strategies to reduce the volume and frequency of wastewater overflows and, hence, reduce human health risks associated with recreational activities in these areas. Acknowledgements Hunter Water Laboratories and CSIRO's Marine and Freshwater Research division (Hobart) are acknowledged for their assistance with sample collection and laboratory analysis of environmental water samples. Assistance with review from a number of individuals within Hunter Water Corporation is gratefully acknowledged.
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