Small-scale wastewater treatment systems: a comparative analysis (2014-2017)

In this project different methods for on-site wastewater treatment are compared using sustainability criteria.

Small-scale wastewater treatment (up to 50 pe) in Sweden’s sparsely populated areas is often poor. Some facilities feature only a septic tank and lack secondary treatment, others perform ineffectively due to high age or insufficient maintenance. The discharge from these small facilities contributes to Sweden being a significant discharger of nitrogen and phosphorus to the Baltic Sea.

When a new wastewater system is to be built there are many treatment units to choose from on the market. For private property owners as well as for the supervising authority it is difficult to assess which technique is most appropriate. It is unclear which system is most sustainable, functional, robust and cost-efficient under different conditions.

The aim of this project is therefore to analyse different techniques for small-scale wastewater treatment using criteria such as sustainability, treatment performance, legal requirements and costs. We use multi-criteria analysis to assess the techniques’ suitability according to pre-defined criteria. This comparison aims to aid the selection of the most appropriate method in the future. In this way, energy consumption and the discharge of nutrients (and thus eutrophication) from small facilities can decrease, and the recycling of nutrients from wastewater could increase.

The project is a collaboration of Luleå University of Technology and Urban Water Management Sweden AB and is funded by J. Gust. Richert Foundation.

Inga Herrmann and Annelie Hedström