Operational residual risk assessment for the Bolivar ASR recycled water project

[摘要] The horticultural activities in the Northern Adelaide Plains (NAP) of South Australia have traditionally used groundwater supplies for irrigation. Expansion of horticulture in the area needed additional water supplies and the Bolivar Wastewater Treatment Plant (WWTP) effluent was identified as a possible source. To reach the appropriate quality, the effluent required tertiary treatment (Dissolved Air Flotation/Filtration; DAFF) including chlorination. Since 1999, the water produced by these treatment processes has been supplied for irrigation via the Virginia Pipeline Scheme (VPS). The demand for water displays a strong seasonal profile with highest demand in summer, therefore, additional storage is needed to balance the demand and supply profiles.The Bolivar Aquifer Storage and Recovery (ASR) project was developed to determine whether tertiary-treated wastewater can be stored in an aquifer and be recovered later for irrigation purposes to provide the additional storage needed at the site. The Bolivar ASR project involved storing surplus water produced during winter in an aquifer as a feasible option to augment DAFF production and meet increases in peak summer demand.Using treated wastewater stored in the Tertiary aquifer at Bolivar, despite the high quality of treatment, involves a potential risk to human health and the environment. Thus, a comprehensive risk assessment was deemed necessary. The Australian Guidelines for Water Recycling: Managed Aquifer Recharge (‘MAR Guidelines’; NRMMC-EPHC-NHMRC, 2009) have been applied to the Bolivar ASR system to assess the risk posed by the injection of treated wastewater into the aquifer. The present risk assessment report follows (and updates) previous risk assessments for the Bolivar ASR recycled water system (Dillon et al., 1999; Dillon et al., 2001; Martin and Dillon, 2005), following the procedures recommended in the Australian Guidelines for Water Recycling (AGWR; NRMMC-EPHC-AHMC, 2006) and the MAR Guidelines.Risks were assessed for the Bolivar ASR system for the twelve hazards identified in the MAR Guidelines. Of these, pathogen and salinity hazards received increased attention as it became evident that these carried a higher level of risk based on the information available. The lack of pathogen data and the variability of indicator organism data already monitored at the Bolivar ASR site necessitated a quantitative microbial risk assessment (QMRA), which considers the index pathogens (Rotavirus, Cryptosporidium and Campylobacter) as recommended in the Australian Guidelines for Water Recycling (AGWR).The probabilistic QMRA mean results indicated that the residual risks posed by the microbial hazards were acceptable (10-6 DALYs), using the DAFF-treated and chlorinated water or the recovered water from the aquifer. The subsurface treatment proved to be an additional barrier to further reduce the risk. Salinity was not decreased along the treatment train, and injection into the aquifer may further increase the salinity. As such, salinity needs to be managed through good irrigation practices and a risk management plan, including selection of the most appropriate crops and monitoring the salinity in the irrigated soil to avoid a future decrease in productivity.

[发布日期] 2010-10-27 [发布机构] CSIRO

[效力级别] Water Resources Engineering [学科分类] 地球科学(综合)