The reduction of perchlorate anions in tap water using a fluidized bed bioreactor

Abstract

The compounds that mainly interfere with perchlorate reduction in contaminated tap water, nitrate and dissolved oxygen (DO), were reduced using a fluidized bed bioreactor. Nitrate was reduced to below the maximum level of contamination adopted by the United StatesEnvironmental Protection Agency (EPA), 10 ppm, and the percentages of nitrate were 90, 84 and 80% for concentrations (conc.) of 25, 50 and 100 ppm perchlorate, respectively, after a 6 h hydraulic retention time (HRT). The DO concentration was reduced to less than 1 mg/L, which is considered to be appropriate for the maximum rates of perchlorate anion reduction, and the percentages of DO removed were 80, 83, and 88% for 25, 50, and 100 ppm perchlorate, respectively, after a 6 h HRT. The maximum reduction for perchlorate was obtained with an HRT of 6 h for the different concentrations of perchlorate anion contamination. This result was confirmed by increase in the concentration of free chloride and decrease in the pH values for UP water. The free chloride concentrations increased to 36, 47 and 58 ppm for the 25, 50 and 100 ppm perchlorate concentration, respectively, after the 6 h HRT. The pH values decreased to 6.01, 5.8 and 6.2 for the 25, 50 and 100 ppm perchlorate concentration, respectively, after the 6 h HRT. Key words: Fluidized bed bioreactor, free chloride, granular activated carbon, water treatment, perchlorate anion.