UPPGRADERING AV SLAMAVSKILJARE GENOM TILLBYGGNAD AV BIOLOGISKA BEHANDLINGSSTEG / Upgrading of small wastewater treatment plants by using biological treatment
The Municipality of Skelleftea is responsible for the operation of several small wastewater treatment plants with insufficient removal of organic matter and nutrients. The small wastewater treatment plants normally consist of septic tanks. A common solution to improve the removal efficiency of small plants is to build infiltration beds. However, due to local conditions this is not always possible. Thus, in this project a strategy involving the installation of biological treatment steps within existing septic tanks has been tested. Two plants were equipped with trickling filters, one plant was equipped with a submerged aerated biological filter and one plant was rebuilt to include a sequencing batch reactor (SBR). Due to diluted and relatively cold inflow to the treatment plants the effect of the installation of biological treatment steps was small. Thus, the results demonstrate the importance of characterising the inflow to a treatment plant and investigating the condition of the sewer system before making suitable improvements.