Valuing decentralized wastewater technologies: a stated preference analysis of advanced and cluster septic systems

Decentralized wastewater treatment systems are key to safe and reliable water access and climate resilience. They provide people with important infrastructure in areas where centralized sewerage is not feasible. While the technology behind traditional septic systems is mature, it has significant flaws leading to nutrient and pathogen release, especially when exposed to changing environmental conditions. Alternatives to traditional septic systems that are more effective at removing nutrients from wastewater have seen limited uptake. Some of these systems, advanced treatment systems, include an additional treatment step for increased treatment efficiency, so do cluster septic systems, which additionally serve multiple homes at once. Using the contingent valuation method, this paper contributes to existing literature by examining individual homeowner preferences and willingness to invest in an alternative onsite wastewater treatment system (OWTS) in the United States, focusing on advanced septic and cluster septic systems. Study respondents positively value both technologies. Specifically, valuation of advanced septic systems is significantly higher than for cluster septic systems. However, respondents asked to contemplate a new house purchase are willing to pay more than people who are asked to replace their existing system. This difference is statistically significant for advanced, but not for cluster septic systems. Our results can aid the development of policies to reduce nutrient inputs from existing and new OWTS by pointing wastewater professionals and policymakers towards areas where investment is most effective.