Aerobic and anaerobic biodegradation of nitrilotriacetate in subsurface soils

Studies were conducted to characterize mineralization of nitrilotriacetate (NTA) in subsurface soils under aerobic and anaerobic conditions. Chemical (redox indicator, resazurin) and biological (dentrification) markers were used as indicators of anaerobic conditions in the test system. The indigenous microflora in subsurface soils previously exposed to septage containing NTA were able to rapidly mineralize NTA under aerobic and anaerobic conditions. The half-lives (t1/2) of mineralization for NTA in aerobic soils ranged from 87 to 160 hr. Biodegradation of NTA under anaerobic conditions where NO3- indicates that a mechanism exists for the anaerobic biodegradation of this substrate. NTA biodegradation can occur readily in the absence of molecular oxygen and the NTA-monooxygenase which are required for the aerobic mineralization of this substrate. These results provide the first evidence that the indigenous microflora in subsurface soils of septic tank tile fields can rapidly degrade NTA under anaerobic conditions.