Inhibition of nitrate and the accumulated denitrification intermediate (nitrite) on perchlorate bioreduction

Abstract

Bioreduction of perchlorate and nitrate by perchlorate-reducing microorganisms (PRMs) is an environmentally friendly, economic, and efficient technology to treat mixed plumes composed of these substances. The influence of perchlorate, nitrate, and denitrification intermediates on PRM activity is a critical factor, which may affect the efficiency of treatment technology. This study investigated the inhibition of nitrate and the intermediate (nitrite) accumulated during the denitrification process on perchlorate bioreduction via a batch-type experiment. From the experiment, it was found that perchlorate had no effect on the denitrification process and that the reduction rate of perchlorate could be improved when NO 3 − -N/ClO 4 − ≤1.2. However, a negative effect of nitrate on perchlorate reduction was observed when NO 3 − -N/ClO 4 − >1.2 with an accumulation of 18.0 mg NO 2 − -N /L. This negative effect increased with the concentration of nitrate. Moreover, nitrite from the denitrification process had a similar negative effect on perchlorate reduction. Bioreduction of perchlorate was not started until nitrite was totally reduced, and a 2–13 day lag period was observed for perchlorate reduction after nitrite depletion.