Inhibition of perchlorate reduction by nitrate in a fixed biofilm reactor.
Perchlorate and nitrate were reduced simultaneously in fixed biofilm reactors. Reduction of 1000 microg L(-1) perchlorate decreased slightly with the addition of 10-16 mg L(-1) NO(3)-N when excess acetate was supplied while denitrification was complete. When influent acetate was reduced by 50% to well below the stoichiometric requirement, perchlorate reduction decreased by 70% while denitrification decreased by only 20%, suggesting that competition for electrons by nitrate was a factor in inhibition. Reduction of nitrate was favored over perchlorate, even though reactor biofilm had been enriched under perchlorate-reducing conditions for 10 months. When excess acetate was restored, perchlorate and nitrate returned to initial levels. The average most probable numbers of perchlorate- and nitrate-reducing bacteria during excess substrate operation were not significantly different and ranged between 2.0 x 10(5) and 7.9 x 10(5)cells cm(-2) media surface area. The effect of nitrate on chloride generation by suspensions of perchlorate-reducing populations was studied using a chloride ion probe. The rate of reduction of 2mM perchlorate decreased by 30% in the presence of 2mM nitrate when excess acetate was added. When acetate was limited, perchlorate reduction decreased by 70% in the presence of equi-molar nitrate.
Choi
Hyeoksun
H
School of Environmental Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang 790-784, South Korea. choihs@colorado.edu
Silverstein
Joann
J
D018441:Biofilms; D002712:Chlorides / Q000737:chemistry; D004566:Electrodes; D009566:Nitrates / Q000737:chemistry*; D010084:Oxidation-Reduction; D010472:Perchlorates / Q000737:chemistry*
D002712:Chlorides; D009566:Nitrates; D010472:Perchlorates