The interaction between Pseudomonas C27 and Thiobacillus denitrificans in the integrated autotrophic and heterotrophic denitrification process.

Compared to autotrophic and heterotrophic denitrification process, the integrated autotrophic and heterotrophic denitrification (IAHD) shows wider foreground of applications in the actual wastewaters with organic carbon, nitrogen and sulfur co-existing. The efficient co-removal of sulfur, nitrogen, and carbon in the IAHD system is guaranteed by the interaction between heterotrophic and autotrophic denitrificans. In order to further explore the interaction between functional bacteria, Pseudomonas C27 and Thiobacillus denitrifcans were selected as typical heterotrophic and autotrophic bacteria, and their characteristics metabolic responses to different sulfide concentrations were studied. Pseudomonas C27 had higher metabolic activity than T. denitrificans in the IAHD medium with sulfide concentration of 3.12-15.62 mmol/L. Moreover, the fastest sulfide removal rate (0.35 mmol/L·h) was achieved with a single inoculation of Pseudomonas C27. Meanwhile, in mixed inoculant conditions, the interaction between Pseudomonas C27 and T. denitrificans (P:T = 3:1, P:T = 1:1 and P:T = 1:3) yielded the highest sulfide removal efficiency (more than 85%) when sulfide concentration was 6.25-12.5 mmol/L. Additionally, the sulfide removal rate increased with the inoculation proportion of Pseudomonas C27. Thus, this apparent interaction provided a theoretical basis for further understanding and guidance on the efficient operation of IAHD system.

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Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.