AWWA WQTC65871

An ion-exchange resin regeneration process has been developed that directly regenerates ion exchange (IX) resins contaminated with perchlorate and nitrate. The process consists of directly contacting perchlorate/nitrate-contaminated ion exchange resin with a perchlorate/nitrate-reducing microbial enrichment culture under anoxic/anaerobic conditions leading to conversion of the perchlorate and nitrate loads on the resin to innocuous chloride and nitrogen gas, respectively. Bioregeneration tests were performed using spent resins loaded in the laboratory with known amounts of perchlorate and nitrate. At prescribed intervals, samples of the resin were taken and eluted for perchlorate and nitrate analysis. The results show that both nitrate and perchlorate were removed from the resin. After two days of operation, about 50% of the perchlorate and 80% nitrate were removed. After six days of operation more than 80% of nitrate and 90% of the perchlorate were removed from the resin. Biofouling removal and of the bioregenerated resin was accomplished using various foulant agents and disinfectants. The results of the research confirm the feasibility of biological regeneration of ion-exchange resins contaminated with perchlorate and nitrate. The process developed has several advantages. The first is conversion of the contaminant perchlorate and nitrate to innocuous chloride and nitrogen gas, respectively. This is in contrast to simply transferring the contaminants to the brines. The second advantage is that biotreated resins can be reused several times, minimizing the cost to water utilities. Lastly, the process is environmentally sustainable because it eliminates the one-way use of resins, thereby minimizing the use of raw materials and energy needed to manufacture new resins. Includes 23 references, figures.