Characteristics of bacteria showing high denitrification activity in saline wastewater

AIMS: Denitrification efficiency at 10% salinity was compared with that at 2% salinity. The characteristics of bacterial strains isolated from the denitrification system, where an improvement of denitrification efficiency was observed at a high salinity were investigated. METHODS AND RESULTS: Two continuous feeding denitrification systems for saline solutions of 2% and 10% salinity, were operated. Denitrification efficiency at 10% salinity was higher than that at 2% salinity. The bacterial strains were isolated using the trypticase soy agar (TSA) medium at 30 degrees C. The phylogenetic analysis of 16S rRNA gene sequences of isolates indicated that halophilic species were predominant at 10% salinity. CONCLUSIONS: The improvement of denitrification efficiency at a high salinity was demonstrated. The strains isolated from the denitrifying system with 10% salinity were halophilic bacteria, Halomonas sp. and Marinobacter sp., suggesting that these bacteria show a high denitrifying activity at 10% salinity. SIGNIFICANCE AND IMPACT OF THE STUDY: The long-term acclimated sludge used in this study resulted in high denitrification performance at a high salinity, indicating that the design of a high-performance denitrification system for saline wastewater will be possible.