H. J. Fallowfield, P. Young, N.J. Cromar and N. Buchananⱡ,
Health and Environment Group, School of the Environment, Flinders University, GPO Box 2100, Adelaide 5001, South Australia
Many rural communities in South Australia depend upon Community Wastewater Management Schemes (CWMS) for their wastewater treatment. On-site septic tanks effect pre-treatment, the treated liquid phase is reticulated to a centralised, 5 cell waste stabilisation pond systems (WSP) for further treatment before disposal for beneficial reuse. High rate algal ponds (HRAP) offer similar or improved wastewater treatment within a smaller footprint making them more attractive where available land is limited. This study presents an overview of the research initially conducted to support acceptance of HRAP technology and to achieve validation by the regulatory agency. An initial lesson learned during the HRAP commissioning phase was that more attention should be afforded to the estimation of dry weather flows in unsewered communities, since only 20% of that estimated eventuated as influent to the CWMS. The research completed at Kingston on Murray and Lyndoch, South Australia clearly demonstrated that HRAPs could provide treatment comparable with that of larger facultative and maturation ponds within a CWMS. Subsequently, the potential benefit of operating HRAPs in series was demonstrated. Independent validation of disinfection performance was assessed by the determination of log10 reduction values (LRV) of Escherichia coli and F-RNA bacteriophage. Aerobic spore forming bacteria were included in the validation as surrogates for pathogenic protozoa. However, they were shown to be inappropriate indicators for the validation of ‘natural’ wastewater treatment systems, highlighting the need to identify other suitable surrogates for pathogenic protozoa. We consider this to be the first time that HRAPs have received regulatory approval which has resulted in the publication of design guidelines for consultant engineers. This 10 year journey should facilitate wider implementation of the technology, initially within the rural communities in South Australia, however, this validation should also be a catalyst for wider implementation of HRAP technology, since the validation process was consistent with national and international guidelines.