Biodegradation of EDTA in pulp and paper mill effluents by activated sludge

Ethylenediaminetetraacetic acid (EDTA) is used to control metal ions in pulp and paper processing. It is water-soluble and therefore released with effluents. EDTA can be removed in activated sludge systems operated under alkaline conditions. The kinetics of EDTA degradation were studied. Activated sludge appeared to degrade EDTA via ethylenediaminetriacetate (ED3A). The ED3A was split into biodegradable iminodiacetic acid and iminoacetaldehydeacetate. The effects of counter ions on the degradation of EDTA by EDTA-grown activated sludge were studied by monitoring the oxidation rate of different EDTA complexes. EDTA-grown activated sludge was capable of oxidizing EDTA under neutral conditions. Conventional activated sludge plants could be adapted to the biodegradation of EDTA through bioaugmentation.