Emission factors and sources of ethylene-diaminetetraacetic acid in waste water––a case study

Ethylene-diaminetetraacetic acid (EDTA) is a complexing agent and has the ability to form stable water-soluble complexes with metal ions. It is used in a variety of industrial applications including pulp and paper, metal, textile, leather rubber, pharmaceuticals, food, polymer production and others. Most of these applications are water based and lead to emissions into the waste water and reach sewage treatment plants. Industrial sources and municipal waste waters were monitored simultaneously. Mixed samples were taken over periods of one week at nine sample sites. The concentrations of EDTA were measured in waste water samples by gas chromatography using N-selective detection. The results showed that, although, the concentrations and loads were variable the paper manufacturing industry was the major EDTA contributor to the influent of the waste water treatment plant and contributed more than 98% of the total load. All the other sources including two household areas, were comparably low. In waste water of households concentrations between 10 and 70 μg/l EDTA could be detected. Concentrations of EDTA from different industrial waste water sources ranged from 28 up to 3980 μg/l. Influent and effluent concentrations of the WWTP were usually high in the range of 500–940 and 390–760 μg/l; respectively. Elimination rates averaged 15%, the calculation is based on emission loads. Specific emission factors were calculated based on population equivalents.