Health risks associated with sewage effluent reuse : case study of the Riverside Golf Course, Tasmania

This thesis conducts an international review of research regarding the public health risks associated with using municipal sewage treated effluent on publicly accessible land and provides an account of a case study that monitored the prevalence and persistence of faecal organisms irrigated onto a golf course. It examines in detail the quantitative risk assessment process developed by risk managers in public health that is used as a tool to predict the likelihood of exposed groups of people to pathogens that may exist in the effluent. From the literature review, researchers have identified new waterborne pathogens that are resistant to conventional forms of disinfection, persist long enough in the environment to reach a potential human host and require only few in number to cause an infection. Relevant international and national wastewater reuse guidelines are also reviewed to highlight methods employed by risk managers to minimise the risks of infection as a consequence of wastewater reuse. A comprehensive survey of current and proposed reuse schemes in Australia was also conducted to help ascertain the growth and the extent of reuse practices in the country. It was found that over the last 13 years the proportion set aside for intentional reuse of the total sewage volumes treated has almost doubled from 3.8 to 6.9% and will continue to grow in the near future. Most of this has been utilised for greenspace or agricultural irrigation where there will be some degree of public contact with the effluent. Because of the current growth of reuse schemes and the prevalence of these new pathogens found in sewage it is prudent to conduct further environmental sampling for these high risk pathogens so that more informed risk assessments can be estimated. A case study was conducted to identify persistence of faecal coliforms/Escherichia coli (FC/E. coli) pathways and persistence at the Riverside Golf Course, Launceston, Tasmania which uses chlorinated secondary treated sewage effluent supplied by the West Tamar Council for irrigation during warm dry weather (October 1995 - April 1996). The effluent is pumped to a temporary holding pond colonised by water fowl and is then spray-irrigated by pop-up sprinklers at a rate of approximately 5 mm for the fairways and 29 mm for the greens per week. Potential routes of transmission of FC/E. coil are discussed and a health risk assessment is presented. Three rounds of FC/E. coil sampling were conducted on the 11-12/10/1995, 8-9/11/1995 and the 26-27/3/1996. Samples of the sewage treatment plant (STP) effluent and holding pond water were collected before and during irrigation. At 9 sites on the first five holes (fairways and greens) samples of the irrigant, creek water, turfgrass, topsoil, golf balls, players' hands and aerosols were collected before and after irrigation. Irrigant water, turfgrass and topsoil were sampled in the early morning; golf balls, players hands and aerosols in the morning, midday and afternoon; and creek samples in the afternoon. Samples were analysed using the membrane filtration technique with the exception of the aerosols which were collected onto agar strips using a high volume centrifugal sampler. Various meteorological, and physicochemical parameters were also monitored. It was found that the STP effluent entering the holding pond had low counts of FC (xvÉvë =14 cfu/100 mL, 95% range = 0 - 8 460 cfu/100 mL). The holding pond samples had considerably higher counts of FC/E. coli = 1 840 cfu/100 mL, 95% range = 372 - 9 120 cfu/100 mL) attributed to the birdlife present. The irrigant samples contained similar high levels of FC/E. coli (xvÉvë = 945 cfu/100 mL, 95% range = 187 - 4 760 cfu/100 mL). Meaningful results of the levels of faecal coliforms on the turfgrass were only available for the third sampling round (Result Table 2.3). The mean value of FC/E. coli on turfgrass was 391 cfu/100 mL eq. (equivalent) after irrigation, which was significantly higher (t\\(_{1,16}\\) = -2.027, P = 0.0386) than the value before irrigation, 75.2 cfu/100 mL eq., indicating that the practice of irrigation significantly increases the presence of FC/E. coil on the turfgrass. In contrast, the FC/E. coil counts were undetectable in almost all samples of soil, players' hands, golf balls and aerosols, in almost all samples of soil, players' hands, golf balls and aerosols. Creek water samples bore several positive results but tended to be low and due to external contamination. The meteorological and physico-chemical analysis revealed a strong correlation between soil moisture and the presence of FC/E. coil in the soil. Despite the fact that the holding pond faecal bacteria levels exceeded the Tasmanian Department of Environment and Land Management's (1994) Guidelines for Re-use of Wastewater in Tasmania mean limit of 750 FC/100 mL from five samples, dieoff was quite rapid indicating that this practice of wastewater reuse presents minimal health risks to golfers and groundstaff in terms of indicator FC/E.coli counts. However, it must be borne in mind that actual pathogens potentially present in effluent are not always adequately indicated by the faecal coliform group, especially viruses and protozoa which need further research as to their prevalence and persistence in the irrigated effluent. In addition, further research needs to be undertaken into the likelihood of the water fowl being a vector opportunity for disease with particular attention being paid to the increased risks associated with the potential disturbance of the holding pond sediment.