Effect of C/N ratio, temperature, pH on autotrophic denitrification rate with hydrogen gas, iron (II) and sodium sulfide as electron donors

Nitrate is considered to be one of the most widely present pollutants leading to eutrophication of environment. The purpose of this work was to isolate and identify new anaerobic denitrifying bacteria from reservoir sediments and utilize different electron donors for isolates to improve nitrate removal efficiency. Using traditional enrichment approach, one purified anaerobic bacterium (Y12) capable of NO₃^--N removal from sediments was obtained. The species identity of Y12 was determined via 16S rRNA gene sequence analysis to be Acinetobacter. In this work, the fastest denitrification rates were observed with ferrous iron as electron donor. And, slightly slower rates were observed with hydrogen and sodium sulfide as electron donors. However, when used hydrogen gas, ferrous iron and sodium sulfide as electron donors, C/N ratios had little effect on autotrophic denitrification rate at the initial C/N ratio from 1.5 to 9.0. Meanwhile, when made use of hydrogen gas, ferrous iron and sodium sulfide as electron donors, a maximum nitrate removal ratio of 100.00%, 91.43% and 87.99% at the temperature of 30℃, respectively. Moreover, maximum denitrification activity was observed at pH 6.0-7.0.