Perchlorate reduction in a hydrogen-based membrane-biofilm reactor

The perchlorate anion (CIO₄-) has been found in potentially harmful concentrations in numerous water sources. Because perchlorate is not removed by conventional water treatment processes, new treatment processes are needed. Biological perchlorate reduction is a promising alternative. The authors investigated a hydrogen-oxidizing hollow-fiber membrane-biofilm reactor system for perchlorate removal. Hydrogen is an ideal electron donor for biological drinking water treatment because it presents no toxicity, is inexpensive, and is unlikely to persist as a source of biological instability in distributions systems. The reactor delivers hydrogen in an efficient and safe manner. Results showed that biological perchlorate reduction takes place concurrently with nitrate reduction, no specialized inoculation is required, and perchlorate can be removed to below the preliminary regulatory standards with no chemical addition other than hydrogen gas. The optimal pH is 8, and the accumulation of intermediates is unlikely. Full denitrification and pH control may be required for excellent perchlorate removal.