Evaluation of full-scale vertical peat biofilters for treatment of septic tank effluents

摘要

The performances of single-pass vertically loaded fibrous peat biofilters treating septic tank wastewater from a single household (pe 6) and a small rural housing estate (pe ～100) are compared. Both systems achieved ＞90% BOD removal and consistently low suspended solids ＜11mg L~(-1). Pathogen removal was generally ＞95% but inconsistent. Nitrification was linked to temperature with removal rates seasonal (50-98%) with no denitrification; this resulted in final effluents with either high NH_4 or NO_3 concentrations, both unsuitable for discharge to surface or ground waters. Phosphorus removal was generally poor. The filters responded poorly to sudden increases in hydraulic loading, causing a reduction in BOD removal in particular. Subsequent soil treatment of effluents after filtration caused a small decrease in both physicochemical and microbial quality. Single-pass vertical peat filters cannot meet the more stringent EU nutrient and microbial standards required for on-site treatment without tertiary treatment to ensure full compliance.