Author(s)

M. Öövel, R. Tarajev, A. Kull & Ü. Mander

Abstract

In August-October 2002 we used an experimental plot established in a seminatural sedge-willow dominated floodplain peatland on the Valgejõgi River, Estonia, to study the purification of effluents from a conventional sewage treatment plant treating municipal wastewater from the town of Tapa and effluents from a distillery in Moe village (about 25000 pe). From the early 1960s to 1997, over 18 ha of this floodplain was used for the treatment of raw wastewater from Tapa and Moe. The retention of organic matter (BOD5), mineral nitrogen (N), and total phosphorus (P) during the vegetation period was 96, 98, and 88%, and in winter 56, 62, and 27% respectively. Due to the very high initial load, however, the river quality downstream worsened. After the construction of the sewage treatment plant in 1997, the water quality improved, although concentrations of Total P (5 mg l-1 on an average) and nitrate N (sometimes <20 mg l-1) in the outflow remain higher than acceptable for sensitive water courses. Thus there is a need for tertiary treatment of purified wastewater. Our experiments on an experimental plot (21×31m, hydraulic load 60 m3 d-1) showed that removal of Total N and Total P was 25-30% and 68-75% respectively. Reduction of NO3-N concentrations was between 50-85%. Keywords: ammonia nitrogen, BOD5, denitrification, floodplain peatland, nitrate nitrogen, total phosphorus 1 Introduction Peat has been widely used in the treatment of wastewaters of various origin and quality. Several laboratory and field experiments show that peat as filter material in trickling filters, biofilters and other conventional treatment systems can effectively mineralize organic material, remove suspended solids and

Keywords

ammonia nitrogen, BOD5, denitrification, floodplain peatland,nitrate nitrogen, total phosphorus