Performance study of biofilter system for on-site greywater treatment at cottages and small households

Abstract

The current contribution of microbial pathogens and nutrient discharge into the environment from inefficient on-site wastewater treatment systems has raised concern in many areas due to the pollution of the nearby water recipient. To overcome this challenge, a novel and more robust proven treatment systems are required. This paper aims to assess the performance of a source separating wastewater management system for the removal of organic matter, total P, total suspended particles and E. coli. The system is a multi-stage approach including – a separate collection of blackwater (BW) and greywater, followed by on-site greywater treatment system in a fixed-film biofilter and finally a soil infiltration system used as a polishing step before discharging into the environment. The separation and collection of BW resulted a notable reduction for chemical oxidation demand (COD), biochemical oxidation demand (BOD), total suspended solids (TSS), nitrogen (N) and phosphorus (P) accounting for 64%, 61%, 75%, 85 and 88%, respectively. The overall removal efficiency of the system for the above-mentioned parameters reached over 90% at the biofilter effluent and more than 95% at the bottom of the constructed infiltration column. For coliform bacteria and E. coli, the overall system reached a reduction of 4–5 log10 units of which the major reduction was observed in the infiltration columns. The effluent quality from this source-separating and multi-barrier biofilter treatment system complies with the Norwegian discharge limits. The assessment results reveal that this system can be used in drinking water source catchments with minimum environmental and health related risks.