The Formation of Intermediates in EDTA and NTA Biodegradation

Widely used anthropogenic chelating agents EDTA and NTA are ubiquitous in wastewaters and natural waters. Chelating agents may enhance the mobility of heavy metals and radionuclides or increase eutrophication. Biodegradation of these chelates may reduce metal mobility, offering a remediation solution. Formation of metabolic intermediates was previously reported during the biodegradation of EDTA and NTA. These intermediates could sequester carbon and electrons, slowing the overall rate of biodegradation. We found accumulation of intermediates was minimal during normal aerobic growth of acclimated cultures on EDTA and NTA. Small levels of intermediates relative to the original amount of chelate were observed to accumulate and persist in systems where biodegradation proceeded in unbuffered systems. Among the metabolic intermediates, ethylenediaminetriacetate (ED3A) is most likely to persist if released into the environment, and can spontaneously cyclize to form the more recalcitrant 3-ketopiperazine-N,Ndiacetate (3KP).