Combining environmental isotopes with Contaminants of Emerging Concern (CECs) to characterise wastewater derived impacts on groundwater quality

McCance, W. and Jones, O. A. H. and Cendon, D. I. and Edwards, M. and Surapaneni, A. and Chadalavada, S. ORCID: https://orcid.org/0000-0002-5000-8313 and Wang, S. and Currell, M. (2020) Combining environmental isotopes with Contaminants of Emerging Concern (CECs) to characterise wastewater derived impacts on groundwater quality. Water Research, 182:116036. pp. 1-15. ISSN 0043-1354


Abstract

The potential for Wastewater Treatment Plants (WWTPs) to cause adverse impacts to groundwater quality is a major global environmental challenge. Robust and sensitive techniques are required to characterise these impacts, particularly in settings with multiple potential contaminant sources (e.g. agricultural vs. site-derived). Stable (δ2HH2O, δ18OH2O, δ15NNO3, δ18ONO3 and δ13CDIC) and radioactive (3H and 14C) isotopes were used in conjunction with three Contaminants of Emerging Concern (CECs) - carbamazepine, simazine and sulfamethoxazole - to discriminate between multiple potential contamination sources at an Australian WWTP. The radioactive isotope tritium provided a sensitive indicator of recent (post-1990s) leakage, with groundwater activities between 0.68 and 1.83 TU, suggesting WWTP infrastructure (activities between 1.65 and 2.41) acted as a recharge ‘window’, inputting treated or partially treated effluent to the underlying groundwater system. This was corroborated by water stable isotopes, which showed clear demarcation between δ18OH2O and δ2HH2O in background groundwater (δ18OH2O and δ2HH2O values of approximately −5 and −28‰, respectively) and those associated with on-site wastewater (median δ18OH2O and δ2HH2O values of −1.2 and −7.6‰, respectively), with groundwater down-gradient of the plant plotting on a mixing line between these values. The CECs, particularly the carbamazepine:simazine ratio, provided a means to further distinguish wastewater impacts from other sources, with groundwater down-gradient of the plant reporting elevated ratios (median of 0.98) compared to those up-gradient (median of 0.11). Distinctive CEC ratios in impacted groundwater close to the WWTP (∼3.0) and further down-gradient (2.7–9.3) are interpreted to represent a change in composition over time (i.e., recent vs. legacy contamination), consistent with the site development timeline and possible changes in effluent composition resulting from infrastructure upgrades over time. The data indicate a complex set of co-mingled plumes, reflecting different inputs (in terms of both quantity and concentration) over time. Our approach provides a means to better characterise the nature and timing of wastewater derived impacts on groundwater systems, with significant global implications for site management, potentially allowing more targeted monitoring, management and remedial actions to be undertaken.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 17 Feb 2022 03:56
Last Modified: 18 Feb 2022 02:34
Uncontrolled Keywords: Contaminant delineation; Contaminants of emerging concern (CECs); Environmental isotopes; Environmental tracers; Wastewater treatment plants
Fields of Research (2008): 05 Environmental Sciences > 0502 Environmental Science and Management > 050206 Environmental Monitoring
Fields of Research (2020): 41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410402 Environmental assessment and monitoring
Identification Number or DOI: https://doi.org/10.1016/j.watres.2020.116036
URI: http://eprints.usq.edu.au/id/eprint/46188

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