Sand filters and drain fields (soil infiltration) are common on-site wastewater treatment techniques in Sweden. However, it is still unclear how the functionality can be effectively assessed. With a qualified assessment advice can be given on how the function can be improved and it can be avoided that units are re-built unnecessarily. In many soil-based treatment units, sludge formation in different parts of the systems has been a concern, e.g. in septic tanks, distribution tanks, distribution and/or aeration pipes. Also, too high water levels in the tanks and problems with the ventilation have been observed. However, it is generally difficult to judge whether these observations have a negative impact on the treatment efficiency. In this project, we review the literature list important factors that affect the performance of soil-based wastewater treatment units. By interviewing authority officials, we will map how supervision is carried out in Sweden and internationally to learn from each other.
The project is funded by the Swedish Agency for Marine and Water Management. It is a collaboration between Luleå University of Technology and RISE (Research Institutes of Sweden).