Cost-effectiveness study of septic tank management in rural communities

The septic tank, as a decentralized solution for sewage treatment, offers an alternative whose maintenance and operation (O&M) costs can be influenced by the chosen management approach. Therefore, this study aims to determine the population thresholds at which the per capita cost of collective management becomes more cost-effective compared to single-family and joint single-family management. The main objective is to contribute to a more sustainable decision-making process regarding sewage collection and treatment systems implemented in rural or decentralized communities. The O&M costs of septic tanks were assessed for three management approaches: collective, single-family, and joint single-family, assuming an average of five inhabitants per household. Non-routine costs encompassed sludge collection, while routine costs involved screen and grit chamber cleaning, sludge and scum inspection and measurement, maintenance of treatment unit structures, analytical control (including physical, chemical, and microbiological analysis) of treated effluent and receiving water bodies, as well as the necessary displacements to carry out these activities. The comparison of management alternatives revealed that the population thresholds at which the cost of collective management with analytical control becomes lower than that of single-family and joint single-family management were found to be 218 and 1168 inhabitants, respectively. For collective management without analytical control, the respective thresholds were 37 and 168 inhabitants. Consequently, the inclusion of analytical control for effluent and water in the receiving body should be carefully evaluated, as it can serve as a limiting factor when selecting collective management as the preferred approach.

Automated summary

This study aims to determine the population thresholds at which the per capita cost of collective management becomes more cost-effective compared to single-family and joint single-family management. The results showed that the population thresholds for collective management with analytical control were found to be 218 and 1168 inhabitants, while without analytical control, the respective thresholds were 37 and 168 inhabitants.