Operational aspects of the desulfurization process of energy gases mimics in biotrickling filters

Biological removal of reduced sulfur compounds in energy-rich gases is an increasingly adopted alternative to conventional physicochemical processes, because of economical and environmental benefits. A lab-scale biotrickling filter reactor for the treatment of high-H₂S-loaded gases was developed and previously proven to effectively treat H₂S concentrations up to 12,000 ppm_v at gas contact times between 167 and 180 s. In the present work, a detailed study on selected operational aspects affecting this system was carried out with the objective to optimize performance. The start-up phase was studied at an inlet H₂S concentration of 1000 ppm_v (loading of 28 g H₂S m⁻³ h⁻¹) and inoculation with sludge from a municipal wastewater treatment plant. After reactor startup, the inlet H₂S concentration was doubled and the influence of different key process parameters was tested. Results showed that there was a significant reduction of the removal efficiency at gas contact times below 120 s. Also, mass transfer was found to be the main factor limiting H₂S elimination, whereas performance was not influenced by the bacterial colonization of the packed column after the initial startup. The effect of gas supply shutdowns for up to 5 days was shown to be irrelevant on process performance if the trickling liquid recirculation was kept on. Also, the trickling liquid velocity was investigated and found to influence sulfate production through a better use of the supplied dissolved oxygen. Finally, short-term pH changes revealed that the system was quite insensitive to a pH drop, but was markedly affected by a pH increase, affecting both the biological activity and the removal of H₂S. Altogether, the results presented and discussed herein provide new insight and operational data on H₂S removal from energy gases in biotrickling filters.