This paper deals with the chemical oxidation to enhance the biodegradability of ethylenediaminetetraacetic acid (EDTA), which is regarded as one of the 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 disposal of such wastewaters came into force in 1995. Therefore, efficient treatment processes are required to remove EDTA from wastewater. In this study, chemical oxidation by Fenton's reagent or ozone was adopted to enhance biodegradability of EDTA followed by semi-continuous BAC treatment. As a result, the biodegradability of EDTA was remarkably enhanced by the chemical oxidation treatment. From the semi-continuous ozone plus BAC treatment, the effectiveness of chemical pretreatment on EDTA removal was observed. The overall removal rate of EDTA increased when the preozonation step was introduced, and more than 80% of EDTA was found to be removed by the ozone plus BAC treatment at the maximum.