Using sediment chemistry to determine the impact of treated wastewater discharge on a natural wetland in New Zealand

Abstract,

Fifteen cores were collected from a wetland and from a stream discharging treated domestic sewage effluent, and analysed for nutrients, major and trace elements to determine the long-term effect of treated wastewater discharge on a natural wetland in the central North Island, New Zealand. Spatial and temporal distribution of Zn, Cu and Pb suggests a recent input most likely related to the operation of the Turangi Wastewater Treatment Scheme and resulting discharge of treated wastewater, as well as road runoff. N and P distribution reflects the influence of effluent discharge but the data also indicate that N content is mainly controlled by the organic matter content in the sediment. Sedimentation rates determined in three of the cores using ¹³⁷Cs are higher in the southern part of the wetland and are associated with high metal concentrations. The study shows that, although the discharge of both treated wastewater and road runoff has an effect on the natural wetland, the impact appears to be mainly confined to the area closest to the point of discharge of the stream into the wetland.