The objective of this project was to demonstrate a novel vessel design and operating practice that can fully utilize the capacity of highly perchlorate-selective ion exchange resin while mitigating other operational problems that often result in premature resin replacement. This was done at three municipalities in Southern California (City of Rialto, City of Colton, and West Valley Water District) at full-scale (1,250 gpm). In addition to minimizing cost, this vessel design is both small in footprint and low in profile, which is beneficial for aesthetics as many of the wells are located in residential areas.
Three demonstrations of the utilization of a novel vessel design and operating practice combined with a highly perchlorate-selective ion exchange resin were undertaken at three municipalities, the West Valley Water District, City of Colton, and City of Rialto, in Southern California. The vessel design combined a lead vessel operated in up-flow mode followed by a polishing vessel operated in down-flow mode. The design provided the capability to remove contaminated resin from the bottom of the lead vessel with replacement of the exhausted resin by uncontaminated resin remaining at the top of the lead vessel and addition of fresh media at the top of the lead vessel. Three operational cycles were completed at the West Valley Water District. Flow balancing issues limited the City of Colton demonstration to two cycles, while several different operational setbacks allowed only one cycle at Rialto.
Each demonstration site had a high volume well (>1,000 gpm) on a groundwater source that had shown persistent perchlorate contamination. Each city had perchlorate in the groundwater at levels between 6-60 ppb. The recommended regulatory level for the state of California was 6 ppb. A brief summary of the performance of the system at each site is provided below:
While operational and equipment difficulties compromised effective contaminant removal to some degree, they did not obviate the economic benefit of the technology. Capital and site preparation costs of approximately $275,000/unit should prove very affordable. Average total annual operating costs were estimated at approximately $77,000/unit with total resin replacement costs of about $110,000 recommended once every three years.