Dennis Gonzalez

Environmental monitoring of selected pesticides and organic chemicals in urban stormwater recycling systems using passive sampling techniques.

Water recycling via aquifers has become a valuable tool to augment urban water supplies in many countries. This study reports the first use of passive samplers for monitoring of organic micropollutants in Managed Aquifer Recharge (MAR). Five different configurations of passive samplers were deployed in a stormwater treatment wetland, groundwater monitoring wells and a recovery tank to capture a range of polar and non-polar micropollutants present in the system. The passive samplers were analysed for a suite of pesticides, polycyclic aromatic hydrocarbons (PAHs) and other chemicals. As a result, 17 pesticides and pesticide degradation products, 5 PAHs and 8 other organic chemicals including flame retardants and fragrances were detected in urban stormwater recharging Aquifer Storage and Recovery (ASR) and an Aquifer Storage Transfer and Recovery (ASTR) system. Of the pesticides detected, diuron, metolachlor and chlorpyrifos were generally detected at the highest concentrations in one or more passive samplers, whereas chlorpyrifos, diuron, metolachlor, simazine, galaxolide and triallate were detected in multiple samplers. Fluorene was the PAH detected at the highest concentration and the flame retardant Tris(1-chloro-2-propyl)phosphate was the chemical detected in the greatest abundance at all sites. The passive samplers showed different efficiencies for capture of micropollutants with the Empore disc samplers giving the most reliable results. The results indicate generally low levels of organic micropollutants in the stormwater, as the contaminants detected were present at very low ng/L levels, generally two to four orders of magnitude below the drinking water guidelines (NHMRC, 2011). The efficiency of attenuation of these organic micropollutants during MAR was difficult to determine due to variations in the source water concentrations. Comparisons were made between different samplers, to give a field-based calibration where existing lab-based calibrations were unavailable.

Microbiological risks of recycling urban stormwater via aquifers for various uses in Adelaide, Australia

This study investigates the potential for an aquifer to provide treatment of stormwater in addition to engineered treatment for the safe use of recovered water for drinking and non-drinking supplies. A brackish limestone aquifer was investigated as a treatment barrier when assessing microbial health-based targets of stormwater harvesting systems. Aquifer treatment was assessed based on pathogen inactivation and attachment to the aquifer sediments. The results showed that the health-based targets for different end uses including open space irrigation, domestic and industrial non-potable uses and drinking water could be met with additional treatment. The aquifer was estimated to have potential for ~4 log10 removal based on inactivation studies and attachment to the aquifer.

Microbiological risks of recycling urban stormwater via aquifers

With the release of the Australian Guidelines for Water Recycling: Managed Aquifer Recharge (MAR), aquifers are now being included as a treatment barrier when assessing risk of recycled water systems. A MAR research site recharging urban stormwater in a confined aquifer was used in conjunction with a Quantitative Microbial Risk Assessment to assess the microbial pathogen risk in the recovered water for different end uses. The assessment involved undertaking a detailed assessment of the treatment steps and exposure controls, including the aquifer, to achieve the microbial health-based targets.

Assessment of treatment options of recycling urban stormwater recycling via aquifers to produce drinking water quality

With the release of the Australian Guidelines for Water Recycling: Managed Aquifer Recharge (MAR), aquifers are now being considered as a treatment barrier when assessing the human health risk of recycled water systems. An MAR research site recharging urban stormwater in a confined aquifer was used in conjunction with a quantitative microbial risk assessment to assess the microbial pathogen risk in the recovered water for drinking. The assessment involved undertaking a detailed assessment of the treatment steps and exposure controls, including the aquifer, to achieve the microbial health-based targets.

Stormwater Quality Review to Evaluate Treatment for Drinking Water Supply via Managed Aquifer Recharge

To date, there is no compiled information for stormwater quality data intended for drinking water supply via managed aquifer recharge (MAR) making risk assessment of these schemes difficult. This study compiles hazards relevant to water recycling via MAR and calculates the associated 95th percentile values. The 95th percentiles of iron, turbidity, colour and faecal indicators exceeded the guideline values at all sites. Likewise, measured hazards for which 95th percentile values met drinking water guidelines (other metals (e.g. zinc), salinity (electrical conductivity) and nutrients including nitrate) did so at all sites. Considering a variety of climatic zones and catchment characteristics and the temporal variations typical in urban stormwater quality, there was a remarkable similarity in the 95th percentile concentrations for a suite of water quality hazards in urban stormwater. This is important in consideration of drinking water risk assessments and determining treatment requirements for potable use.