Assessing relationships between onsite wastewater treatment system maintenance patterns and system-level variables

Kyle N Connelly; Seth J Wenger; Nandita Gaur; Jacob M Bateman McDonald; Mike Occhipinti; Krista A Capps

doi:10.1016/j.scitotenv.2023.161851

Assessing relationships between onsite wastewater treatment system maintenance patterns and system-level variables

Sci Total Environ. 2023 Apr 20:870:161851. doi: 10.1016/j.scitotenv.2023.161851. Epub 2023 Jan 27.

Authors

Kyle N Connelly¹, Seth J Wenger², Nandita Gaur³, Jacob M Bateman McDonald⁴, Mike Occhipinti⁵, Krista A Capps⁶

Affiliations

¹ Odum School of Ecology, University of Georgia, Athens, GA 30602, USA; The River Basin Center, University of Georgia, Athens, GA 30602, USA. Electronic address: kyle.connelly@uga.edu.
² Odum School of Ecology, University of Georgia, Athens, GA 30602, USA; The River Basin Center, University of Georgia, Athens, GA 30602, USA. Electronic address: swenger@uga.edu.
³ Department of Crop and Soil Sciences, University of Georgia, Athens, GA 30602, USA. Electronic address: nandita.gaur@uga.edu.
⁴ Lewis F. Rogers Institute for Environmental and Spatial Analysis, University of North Georgia, Oakwood, GA 30566, USA. Electronic address: jacob.mcdonald@ung.edu.
⁵ Athens-Clarke County Unified Government, Snipes Water Resources Building, Athens, GA 30601, USA. Electronic address: mike.occhipinti@accgov.com.
⁶ Odum School of Ecology, University of Georgia, Athens, GA 30602, USA; Savannah River Ecology Laboratory, University of Georgia, Aiken, SC 29802, USA. Electronic address: kcapps@uga.edu.

PMID: 36709899
DOI: 10.1016/j.scitotenv.2023.161851

Abstract

Globally, millions of households rely on onsite wastewater treatment systems (OWTSs), such as septic systems, to safely treat and dispose of wastewater. Conventional subsurface OWTSs are a common and affordable option for many landowners, and effectively remove pathogenic and nutrient pollution from wastewater when properly sited and maintained. However, OWTSs can also be a source of nonpoint pollution in watersheds when they are not functioning properly. To better understand the drivers of OWTS maintenance and failure, we explored relationships between OWTS age, environmental characteristics (edaphic conditions, topographic wetness index, and distance to stream), and repair and pumping records for OWTSs in Athens-Clarke County, Georgia, USA. Repair records indicated that 7.8 % of the 8826 OWTSs in the study were repaired over a 78-year period and that the median age of a repaired OWTSs was 65 years old. Pumping records showed that 12.2 % of the OWTSs were pumped in a 38-month period (an annualized rate of 5.7 %). The suite of widely available environmental variables we used as predictors were likely not granular enough to detect patterns of individual system maintenance at this scale. However, we found that the oldest OWTSs (>50 years) had the highest probabilities of being repaired and exhibiting signs of hydraulic failure. Notably, new OWTSs (2-10 years) were nearly as likely as the oldest systems to exhibit signs of hydraulic failure. These findings suggest that repair and replacement efforts should target older systems that are at or near the end of their serviceable life, and, in addition to continually monitoring older systems, all OWTSs should be inspected one year after installation. By leveraging data that may already exist, practitioners in other localities can use this reproducible approach to estimate the performance of OWTSs. Our data and methods will support efforts to prioritize wastewater infrastructure investments and policies.

Keywords: Decentralized wastewater infrastructure; Environmental layers; Onsite wastewater treatment systems; Risk management; Septage.