AWWA ACE56242

This paper discusses a collaborative effort between MWH of Pasadena, California and the University of Houston to demonstrate the long-term performance of conventional ion-exchange technology for perchlorate removal, and to evaluate two disparate alternatives (chemical and biological) for brine treatment and reuse. While addressing these objectives, the underlying requirement of the pilot-scale system is to ensure that the treated water perchlorate concentration remains below the recently lowered California Department of Public Health Services perchlorate Advisory Action Level of 4 ug/L. Designed, constructed and installed within MWH's Mobile Water Treatment Pilot Trailer, the pilot plant includes two parallel ion-exchange columns (clear PVC) that can be operated independently in either co- or counter-current exhaustion and regeneration. For the purposes of this study, the columns have been operated in a counter-current mode with up-flow exhaustion and down-flow regeneration. Screens have been inserted at the top and bottom of each ion-exchange column to contain the resin in the column during the exhaustion and regeneration modes. The treated water is collected in a clearwell and is also used for rinse water after regeneration. The spent brine solution can either be wasted or collected in a holding tank to be fed to the brine treatment system. The treated brine is then returned to the regeneration (sweet) brine tank. The chemical brine treatment system, provided by Calgon Carbon Corporation (Pittsburgh, PA), employs a high- pressure and high-temperature catalytic process to reduce the nitrate and perchlorate in the spent brine. After the PNDM, the treated brine is then ready for reuse. The PNDM uses a chemical reductant (ammonia) dose based on the measured concentrations of nitrate and perchlorate in the spent brine. This sequencing batch reactor (SBR) utilizes a culture initially developed from a marine mud inoculum to reduce the nitrate and perchlorate in the spent brine. The SBR headspace is filled with nitrogen to help provide an anoxic environment for the culture during transfers. Filters between the SBR and sweet brine reservoir prevent unsettled biomass from plugging the resin during regeneration. Includes tables, figures.