Septic tanks as a pathway for emerging contaminants to the aquatic environment: need for alternative rural wastewater treatment?

Wilschnack, Maike; Cartmell, Elise; Yates, Kyari; Petrie, Bruce

Abstract

Septic tanks (STs) as a decentralised approach to community wastewater treatment were investigated as a pathway for emerging contaminants (ECs) entering the aquatic environment. A broad range of ECs were examined in five community STs (population equivalents 217 – 475) and receiving rivers in Scotland over 12 months. All 68 studied ECs were detected at least once in ST influent or effluent at a broad concentration range from ng L−1 – μg L−1 which can surpass freshwater predicted no-effect concentrations. Pharmaceuticals with acute use, such as antibiotics and antifungals, had high monthly variability and concentrations can exceed those previously found in centralised wastewater treatment works. Differences between the STs demonstrate the impact of localised prescription and population behaviour on EC concentrations. The similarities in concentrations between influent and effluent, suggest limited or no removal of ECs in STs. Hence, dilution of the discharges is required to mitigate environmental risk. Although the contribution of ECs sorbed to suspended solids to the total EC concentration was generally small (< 10%), higher contributions (> 30%) were observed for fluoroquinolone antibiotics (ofloxacin and ciprofloxacin), antidepressants (fluoxetine), and antifungals (clotrimazole). A wide range of ECs were also detected in rivers upstream and downstream of the ST discharge points, and concentrations increased by up to 95% downstream. In general, risk quotients (RQs) in the rivers were low, indicating small risk for the environment. However, higher RQs (> 1) were found for ibuprofen, diclofenac and ciprofloxacin in a few samples. Therefore, reducing their concentration by improving ST performance or through sustainable medicines use may be needed at low dilution locations to mitigate any risk.

Citation

WILSCHNACK, M., CARTMELL, E., YATES, K. and PETRIE, B. 2024. Septic tanks as a pathway for emerging contaminants to the aquatic environment: need for alternative rural wastewater treatment? Environmental pollution [online], 362, article number 124988. Available from: https://doi.org/10.1016/j.envpol.2024.124988

• Journal Article Type: Article
• Acceptance Date: Sep 16, 2024
• Online Publication Date: Sep 17, 2024
• Publication Date: Dec 1, 2024
• Deposit Date: Sep 18, 2024
• Publicly Available Date: Sep 18, 2024
• Journal: Environmental pollution
• Print ISSN: 0269-7491
• Electronic ISSN: 1873-6424
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 362
• Article Number: 124988
• DOI: https://doi.org/10.1016/j.envpol.2024.124988
• Keywords: Wastewater; Pharmaceutical waste; Rivers; Contaminants; Scotland
• Public URL: https://rgu-repository.worktribe.com/output/2480909
• Additional Information: Following the main text, the file accompanying this record also contains supplementary material that was originally posted separately on the journal website.