Development of cultures capable of reducing perchlorate and nitrate in high salt solutions.

An ion exchange process with biological perchlorate and nitrate destruction and reuse of spent regenerant brine has been proposed as an efficient and environmentally sound method to treat perchlorate-contaminated groundwater. A culture capable of reducing perchlorate and nitrate in spent ion exchange regenerant brine containing at least 30 g/L NaCl is needed for this to be feasible. A batch culture inoculated from activated sludge failed to acclimate to more than 15 g/L NaCl whether nitrate was present or not. A mixed culture inoculated from marine sediment was capable of simultaneously reducing 100mg/L perchlorate and denitrifying 500 mg/L nitrate within 5 h in a synthetic medium in the presence of 30 g/L NaCl. The growth conditions to maintain this culture in a healthy state required the addition of trace metals, Na2S, and phosphate. A second culture capable of removing 100 mg/L perchlorate from synthetic medium containing 60 g/L NaCl within 24 h was also developed.