DECREASED METAL CONCENTRATIONS IN GROUND-WATER CAUSED BY CONTROLS OF PHOSPHATE EMISSIONS

A NEW generation of phosphate-eliminating sewage treatment plants and the recent prohibition of phosphates in detergents have considerably r educed the concentrations of phosphate in surface waters1. But there h as been concern that replacing phosphate in detergents with complexing agents might cause increased mobilization of heavy metals, and corseq uent pollution of ground waters2,3. Here we present a twelve-year anal ysis of phosphate, manganese and cadmium in the river Glatt, Switzerla nd, and in an adjacent aquifer which is infiltrated by the river water . Together with a reduction of phosphate concentrations in both river and ground water over the study period, we find lower groundwater conc entrations of manganese and cadmium. We postulate that lower phosphate levels have decreased the amount of oxidizable organic carbon in the river bed, and hence have created less reducing conditions in the infi ltrating water. This in turn has resulted in decreased reductive disso lution of manganese and cadmium in the ground water. It thus appears t hat eliminating phosphate has led to an unexpected improvement in drin king water quality with respect to heavy metals.