Effect of hydraulic retention time, ZVI concentration, and Fe2+ concentration on autotrophic denitrification efficiency with iron cycle bacterium strain CC76

The immobilized reactor of iron-reducing bacteria and zero-valent iron (ZVI) integrated system was established. This study has shown that the effects of hydraulic retention times (9, 11, 13 h), ZVI concentrations (2, 4, 6, 8 mg/L), and Fe2+ concentrations (5, 10, 15 mg/L) on the denitrification characteristics of iron cycle bacterium strain CC76. The results show that the longer the HRT is, the stronger ability of bacteria to remove nitrate. When ZVI concentration was 4 mg/L and the Fe2+ concentration is 15 mg/L, the removal efficiency of nitrate was the highest, reaching the maximum value of 93.02% (1.07 mg/L/h). Since increasing ZVI concentration in a certain range can not only promote chemical reduction but also make use of strain CC76 as an electron donor. Also, the abundance of strain CC76 decreased with the increase of ZVI concentration, which indicated that adding a low concentration of ZVI could reduce the inhibitory effect on bacteria. Hypothesis analysis of principal components showed that a low concentration of ZVI is beneficial to increase nitrate removal rate. Community structure analysis indicated that strain CC76 and related bacteria were the most abundant bacteria in the reactor.