Reduction of perchlorate by salt tolerant bacterial consortia.

Two perchlorate-reducing bacterial consortia (PRBC) were obtained by enrichment cultures from polluted marine sediments. Non-salt-tolerant PRBC (N-PRBC) was enriched without the addition of NaCl, and salt tolerant-PRBC (ST-PRBC) was enriched with 30 g-NaCl L(-1). Although the perchlorate reduction rates decreased with increasing NaCl concentration, ST-PRBC (resp., N-PRBC) could reduce perchlorate until 75 g-NaCl L(-1) (resp., 30 g-NaCl L(-1)). The reduction yield (1.34±0.05 mg-perchlorate per mg-acetate) and maximum perchlorate reduction rate (86 mg-perchlorateL(-1) h(-1)) of ST-PRBC was higher than those (1.16±0.03 mg-perchlorate per mg-acetate and 48 mg-perchlorate L(-1) h(-1)) of N-PRBC. Kinetic analysis showed that NaCl acted as an uncompetitive inhibitor against both PRBCs. The inhibition constants were 25 and 41 mg-NaCl L(-1) for N-PRBC and ST-PRBC, respectively.

Microbial treatment of high-strength perchlorate wastewater.

To treat wastewater containing high concentrations of perchlorate, a perchlorate reducing-bacterial consortium was obtained by enrichment culture grown on high-strength perchlorate (1200 mg L(-1)) feed medium, and was characterized in a sequence batch reactor (SBR) over a long-time operation. The consortium removed perchlorate in the SBR with high reduction rates (35-90 mg L(-1)h(-1)) and stable removal efficiency over 200-day operations. The maximum specific perchlorate reduction rate (qmax), half saturation constant (Ks), and optimal pH range were 0.67 mg-perchlorate mg-dry cell weight(-1) h(-1), 193.8 mg-perchlorate L(-1), and pH 7-9, respectively. The perchlorate reduction yield was 0.48 mol-perchloratemol-acetate(-1). A clone library prepared using the amplicons of cld gene encoding chlorate dismutase showed that the dominant (per)chlorate reducing bacteria in the consortium were Dechlorosoma sp. (53%), Ideonella sp. (28%), and Dechloromonas sp. (19%).