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Mzyece CC, Glendell M, Gagkas Z, Quilliam RS, Jones I, Pagaling E, Akoumianaki I, Newman C, Oliver DM. Eliciting expert judgements to underpin our understanding of faecal indicator organism loss from septic tank systems. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 921:171074. [PMID: 38378059 DOI: 10.1016/j.scitotenv.2024.171074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 02/05/2024] [Accepted: 02/16/2024] [Indexed: 02/22/2024]
Abstract
Septic tank systems (STS) in rural catchments represent a potential source of microbial pollution to watercourses; however, data concerning the risk of faecal indicator organism (FIO) export from STS to surface waters are scarce. In the absence of empirical data, elicitation of expert judgements can provide an alternative approach to aid understanding of FIO pollution risk from STS. Our study employed a structured elicitation process using the Sheffield Elicitation Framework to obtain expert judgements on the proportion of FIOs likely to be delivered from STS to watercourses, based on 36 scenarios combining: (i) septic tank effluent movement risk, driven by soil hydro-morphological characteristics; (ii) distance of septic tank to watercourse; and (iii) degree of slope. Experts used the tertile method to elicit a range of values representing their beliefs of the proportion of FIOs likely to be delivered to a watercourse for each scenario. The experts judged that 93 % of FIOs would likely be delivered from an STS to a watercourse under the highest risk scenario that combined (i) very high STS effluent movement risk, (ii) STS distance to watercourse <10 m, and (iii) a location on a steep slope with gradient >25 %. Under the lowest risk scenario, the proportion of FIOs reaching a watercourse would likely reduce to 5 %. Expert confidence was high for scenarios that represented extremes of risk, while uncertainty increased for scenarios depicting intermediate risk conditions. The behavioural aggregation process employed to obtain a consensus among the experts proved to be useful for highlighting both areas of strong consensus and high uncertainty. The latter therefore represent priorities for future empirical research to further improve our understanding of potential pollution risk from septic tanks and in turn enable better assessments of potential threats to water quality in rural catchments throughout the world where decentralised wastewater systems are common.
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Affiliation(s)
- Chisha Chongo Mzyece
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, Scotland, United Kingdom of Great Britain and Northern Ireland.
| | - Miriam Glendell
- Environmental and Biochemical Sciences Group, The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, Scotland, United Kingdom of Great Britain and Northern Ireland
| | - Zisis Gagkas
- Environmental and Biochemical Sciences Group, The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, Scotland, United Kingdom of Great Britain and Northern Ireland
| | - Richard S Quilliam
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, Scotland, United Kingdom of Great Britain and Northern Ireland
| | - Ian Jones
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, Scotland, United Kingdom of Great Britain and Northern Ireland
| | - Eulyn Pagaling
- Environmental and Biochemical Sciences Group, The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, Scotland, United Kingdom of Great Britain and Northern Ireland
| | - Ioanna Akoumianaki
- Environmental and Biochemical Sciences Group, The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, Scotland, United Kingdom of Great Britain and Northern Ireland
| | - Claire Newman
- Environmental and Biochemical Sciences Group, The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, Scotland, United Kingdom of Great Britain and Northern Ireland
| | - David M Oliver
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, Scotland, United Kingdom of Great Britain and Northern Ireland
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Iannella M, Fiasca B, Di Lorenzo T, Di Cicco M, Biondi M, Mammola S, Galassi DM. Getting the ‘most out of the hotspot’ for practical conservation of groundwater biodiversity. Glob Ecol Conserv 2021. [DOI: 10.1016/j.gecco.2021.e01844] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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