Bioregeneration of Spent Ion-Exchange Resin Loaded with Nitrate/Perchlorate and Biofouling Removal

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A new process has been developed that regenerates perchlorate/nitrate-contaminated ionexchange resins (IX) biologically without requiring the use of brine. The process consists of directly contacting perchlorate/nitrate-loaded IX resin with a perchlorate/nitrate-reducing microbial culture under anoxic/anaerobic conditions leading to conversion of the perchlorate and nitrate load on the resin to innocuous chloride and nitrogen gas, respectively. A second cycle of bioregeneration was performed using a resin sample loaded in an actual IX plant in California.

At prescribed intervals, samples of the resin were taken and eluted for perchlorate and nitrate analyses. The results show that both nitrate and perchlorate were removed from the resin. After six days of operation only about 20% of perchlorate was remaining and most of the nitrate had been biodegraded. Biofouling was observed after bioregeneration. Several methods including warm and cold salt brine (NaCl) , sodium hypochlorite or peracetic acid solution were investigated for their potential to remove fouling from the resin. The results show that sodium hypochlorite, peracetic acid and heated sodium chloride solutions can effectively remove fouling from the resin. Investigations are underway to examine the possibility of bioregeneration and biofouling removal in multiple cycles.

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