Water and sediment chemistry of a wetland treating municipal wastewater

Abstract

The effects of wastewater discharge in an artificially confined wetland, Turangi land treatment facility, New Zealand, were investigated by measuring the changes in water and sediment chemistry in the land treatment facility. Analysis of surface water shows that the treatment facility is effective at removing BOD 5 (85%), but not NH 4 -N, SO 4 , PO 4 -P, and total suspended solids. Surface flow measurements indicate that the effluent flows through the confined wetland in less than a day. The retention time is too short to allow exchange between wetland vegetation and effluent, thus preventing efficient contaminant removal. The change in land use c. 30 years ago associated with the construction of the land treatment facility is reflected in a change † Corresponding author. M99001Received 15 January 1999; accepted 25 May 1999 in stratigraphy and sediment chemistry. Elevated sulphur and zinc concentrations in sediments are attributed to sewage effluent discharge, and indicate that soil uptake is taking place.