Ethylenediamine tetraacetic acid (EDTA) and diethylenetriamine pentaacetic acid (DTPA) are synthetic chelating agents that form stable complexes with most metals and are used in a variety of industrial applications. They are increasingly used with peroxide and ozone bleaching of wood pulp to sequester iron and manganese. These chelates have been widely reported to either resist degradation or undergo slow biodegradation. EDTA and DTPA have few known environmental impacts in receiving waters.
A study was conducted to assess the biodegradability of EDTA and DTPA and to determine if these compounds could be transformed in conventional effluent treatment processes. Four dissimilar inocula were used in batch and continuous aerobic tests using a variety of enrichment techniques. Selection pressure was applied to bacterial populations by providing EDTA and DTPA as sole carbon sources. Additionally, experiments were conducted using degraders of chemically similar compounds nitrilotriacetic acid and triethanolamine. In all experiments, the results showed that neither EDTA or DTPA are biodegraded under aerobic conditions.