Biodegradation of EDTA in Pulp and Paper Mill Effluents by Activated Sludge Available to Purchase

Activated sludge systems operated under alkaline conditions remove EDTA. To improve EDTA removal a better understanding of EDTA biodegradation and its intermediates as well as knowledge of kinetic parameters are a prerequisite. Activated sludge appeared to degrade EDTA via ethylenediaminetriacetate (ED3A). The sludge was able to split ED3A into readily biodegradable iminodiacetic acid and iminoacetaldehydeacetate. The maximum growth rate of EDTA-grown sludge was approximately 0.15 days⁻¹. The K_m for EDTA and maximum oxidation rate of EDTA-grown sludge were 10 mg/L and 135 mg O₂ g⁻¹ SS day⁻¹. Specially cultivated activated sludge degraded EDTA under neutral conditions and was capable of degrading the FeEDTA complex at a low rate. Bioaugmentation of EDTA-grown sludge enabled EDTA removal in a treatment system under neutral conditions.