Contested Factors for Sustainability: Construction and Management of Household On-Site Wastewater Treatment Systems

On-site sanitation systems experience a high failure rate with resulting environmental and public health implications. In the United States alone, the EPA estimates that 10% of the 26 million homes served by on-site systems have failed. If this failure rate is extrapolated to the 8% of the global population that the UN estimates have gained access to sanitation between 1990 and 2008, an additional 5 million failed systems have been constructed. To address issues like this, development theory currently emphasizes a blend of hardware (e.g., infrastructure, technology) and software (e.g., knowledge, institutions, education) in an effort to achieve sustainable development. However, there is a lack of both theory that addresses this interaction and a definition of sustainable infrastructure. To begin to address this gap, an initial set of 40 factors that may contribute to sustainable on-site sanitation systems was identified from a literature review including the Web of Science, the Engineering Village, and the full record of ASCE from 2000 to July 2011. A panel of 14 experts including academics, regulators, international development practitioners, operation and maintenance (O&M) providers, and manufacturer/designers was then assembled to identify any additional factors that may lead to resilient on-site systems and to evaluate each one using the Delphi method. The panel evaluated each factor iteratively to develop a measure of its importance to the sustainability of on-site sanitation infrastructure. Experts were also invited to provide and review comments explaining or discussing the ratings they provided, and to identify the factors they perceived to be the most and least important. Of the initial list of factors, nine came to consensus as being important or very important, including factors such as owner occupancy, quality of installation or materials, and postconstruction follow-up programs. In addition, 10 factors provoked particularly diverse, or contentious, opinions with ratings that more than doubled the target criteria for consensus. These contentious factors are analyzed to identify trends and debates in expert opinion that showcase future research needs as well as issues that practitioners must address to build sustainable systems.