Charles A. Sprecher¹, Walter Giger and Christian Schaffner²

The environmental aspects od NTA have been thoroughly discussed because of its increasing us as builder components of detergents. EDTA was included in current NTA monitoring programs based on preliminary assessments of the environmental fate of this organic complexing agent. Insuffient biological degradation rates for EDTA in laboratory experiments suggested its refractory behaviour in waste water treatment. In fact, no removal of EDTA was observed in full-scale activated sludge treatment, whereas NTA was eliminated to less than 5%. Consequently, EDTA was also found in river waters at concentrations ranging from 0.5 to 55 mgm^-3 , in significantly higher levels than NTA. In a large European lake EDTA concentrations of 3 to 5 mgm^-3 where observed at various water depths. In contrast, NTA concentrations were approximately 0.5 mgm^-3 in the surface waters and below the detection limit of 0.2 mgm^-3 in samples from greather depths. The hypothesis that EDTA would not be affected during infiltration of river water into ground water was confirmed. EDTA concentrations of 2 to 10 mgm^-3 were detected in ground waters containing large portions of bank filtrated water. It should be noted that in the same sample NTA was not detectable.

The occurence and fate of EDTA in the aquatic environment must certainely be considered in the current discussions about the environmental impact of NTA.