Improvement of biodegradability of ethylenediaminetetraacetic acid in biological activated carbon treatment by chemical preoxidation

This paper deals with the chemical oxidation to enhance the biodegradabilit y of ethylenediaminetetraacetic acid (EDTA), which is regarded as one of th e non-biodegradable substances, as a pretreatment for biological activated carbon (BAC) treatment. The use of EDTA is indispensable in many industries . However, when it is contained in wastewater, difficulty arises concerning treatment because of its stable chemical structure. Wastewaters containing EDTA have been thrown into the ocean, but the prohibition of the marine di sposal of such wastewaters came into force in 1995. Therefore, efficient tr eatment processes are required to remove EDTA from wastewater. In this stud y, chemical oxidation by Fenton's reagent or ozone was adopted to enhance b iodegradability of EDTA followed by semi-continuous BAC treatment. As a res ult, the biodegradability of EDTA was remarkably enhanced by the chemical o xidation treatment. From the semi-continuous ozone plus BAC treatment, the effectiveness of chemical pretreatment on EDTA removal was observed. The ov erall removal rate of EDTA increased when the preozonation step was introdu ced, and more than 80% of EDTA was found to be removed by the ozone plus BA C treatment at the maximum. (C) 1999 Elsevier Science B.V. All rights reser ved.