Biological reduction of perchlorate in ion exchange regenerant solutions containing high salinity and ammonium levels

Abstract

The most promising technologies to remove perchlorate from water are ion exchange and biological reduction. Although successful, ion exchange only separates perchlorate from water; it does not eliminate it from the environment. The waste streams from these systems contain the caustic or saline regenerant solutions used in the process as well as high levels of perchlorate. Biological reduction could be used to treat the regenerant waste solutions from the ion exchange process. A treatment scheme, combining ion exchange and biodegradation, is proposed to completely remove perchlorate from the environment. Perchlorate-laden resins generate brines containing salt concentrations up to 6% or caustic solutions containing up to 0.5% ammonium. Both, high salt and ammonium hydroxide concentrations are potentially toxic to microorganisms. Therefore, the challenge of the proposed system is to find perchlorate reducing microorganisms that are effective under such stressful conditions. Preliminary results have shown that salt concentrations as low as 0.5% reduced the perchlorate biodegradation rate by 30%; salt concentrations greater than 1% decreased this rate to 40%. Although biodegradation was seen in ammonium levels of 0.4%, 0.6% and 1%, the perchlorate biodegradation rate was 90% of that at 0% ammonium hydroxide. Further research will focus on the isolation and/or acclimation of microorganisms that are able to biodegrade perchlorate under these stressful conditions.

Microbial Degradation of Perchlorate: Principles and Applications

“…In the case of an anion exchange process, the regeneration of the resin typically generates a 7-12% NaCl brine solution enriched in perchlorate. Gingras and Batista (2002) were unable to adapt a PRB culture to degrade perchlorate in an ion exchange brine. As little as 1% NaCl reduced perchlorate reduction rates by their perchlorate-degrading culture by half (Gingras and Batista, 2002).…”

“…Gingras and Batista (2002) were unable to adapt a PRB culture to degrade perchlorate in an ion exchange brine. As little as 1% NaCl reduced perchlorate reduction rates by their perchlorate-degrading culture by half (Gingras and Batista, 2002). High NaCl systems may not be required for certain types of specialized ion exchange resins.…”

Rapid and complete destruction of perchlorate in water and ion-exchange brine using stabilized zero-valent iron nanoparticles

“…However, these technologies are limited by some critical technical and/or economic drawbacks such as slow degradation kinetics and production of large volumes of concentrated process waste residuals. For instance, IX has been considered as one of the best available technologies for perchlorate removal (Gingras and Batista, 2002), and many commercial IX resins can offer high perchlorate sorption capacity. However, the regeneration efficiency of the IX resins has been found to be prohibitively poor.…”

“…On the other hand, it is practically very desirable to destroy perchlorate in saline water or spent IX brine, where high concentrations of perchlorate are co-present with high concentrations of chloride and/or other salts (Gingras and Batista, 2002;Xiong et al, 2006). , respectively, a 22% and 50% increase compared with that when Cl À was absent.…”

Natural Attenuation of Perchlorate in Groundwater: Processes, Tools and Monitoring Techniques

“…Perchlorate-reducing organisms are widespread in the environment (Coates et al, 1999;Logan, 2001), including pristine and hydrocarboncontaminated soils, aquatic sediments, and industrial and agricultural waste sludges (Gingras and Batista, 2002 …”