Assessing Health Risks from Pesticides in Recycled Water: A Case Study of Augmentation of Drinking Water Supplies in Perth, Western Australia

ABSTRACT

A characterization of pesticides in secondary treated effluent (STE) and a screening health risk assessment were conducted to evaluate potential health impacts of recycled water for potable reuse. Samples of STE were examined pre- and post-reverse osmosis (RO) treatment in two plants. Risk quotients (RQ) were estimated by expressing the maximum and median concentration as a function of the health value. Of 128 pesticides analyzed, 11 were detected in STE. Trifluralin was detected in 86.5% of the STE samples followed by metolachlor (67.6%), 2,4-D (50%), and propiconazole (42.5%). Metolachlor was the only pesticide detected post-RO in one sample (0.08 μg/L, limit of reporting = 0.05 μg/L). RQ(max) were all below health values in the STE with the exception of thiophanate methyl (RQ max = 2.4). RO was able to reduce the concentration of all pesticides below LOR. Median removal efficiency for RO ranged from 67.1% (atrazine) to 98.8% (2,4-D). The results indicate that, despite the detection of pesticides in STE, the impact on indirect potable reuse is negligible due to the low concentrations in STE and their subsequent removal during RO treatment. Implementation of risk management strategies to optimize safety and recommendations for a monitoring program are also discussed.

Key Words:

• water recycling
• water quality
• organic pollutants
• indirect potable reuse

ACKNOWLEDGMENTS

This research was conducted as part of the Premiers Collaborative Research Project (PCRP), a collaborative effort between Department of Health, Department of Water, Department of Environment & Conservation, Water Corporation of Western Australia, The University of Western Australia, Curtin University of Technology, Chemistry Centre WA, and the National Measurement Institute (NMI). State government funding was provided by the Office of Science & Innovation. Acknowledgment is also extended to Karyn Courtney and Clare Newby from ChemCentre for the analysis of the samples, and Palenque Blair from the Water Corporation for providing technical support during the project.