Domestic on-site wastewater: Real needs and relative risks

This paper reviews the literature and identifies some of the gaps and imbalances in current practices of the various on-site wastewater stakeholders. A primary gap identified is the low level of end-user representation in the shaping of policy and industry activities. Adaptive management, research and development and improved understanding of end-users through monitoring and evaluation, are likely to contribute to the effective design, implementation, and sustainability of OWTS, as well as improving processes, and compliance regarding regulatory requirements.

It is argued that the resilience of treatment systems is intrinsically related to the risk of incidents. The more resilient a treatment system is, the greater range of conditions can be dealt with successfully without incidents arising. The focus on N reduction for on-site wastewater treatment units is weakly justified in the context of the real and relative risks the N emissions present. It is a distraction from where the on-site wastewater industry should be putting its efforts to mitigate the real risks and to provide improved levels of service to the end-user of these systems.

Our assessment is based on a decade of designing and implementing onsite wastewater systems in the field, a formal snapshot survey of 20 end-users survey and a review of the literature. Some end-users want to be less constrained by over regulation in adopting innovative management systems while in contrast regulators, backed with improved science, are increasingly concerned about risks.

Public good scientific research of appropriate and resilient on-site wastewater technologies, treatment processes and management systems is recommended in parallel with a thorough study and development of the appropriate indicators and design principles for OWTS, to guide future monitoring and evaluation of OWTS. We conclude that an explicit focus on adaptive management where there is collegial interaction and ongoing mutual learning between design engineers, manufacturer and regulators would enable better practice to become developed most efficiently. In addition, if the same attentiveness was applied to research supporting the effective monitoring and evaluation clients’ needs and concerns, which were explicitly incorporated into the adaptive management process, progress may develop more quickly.