Operational aspects, pH transition and microbial shifts of a H2S desulfurizing biotrickling filter with random packing material.

Abstract Pall rings, a common random packing material, were used in the biotrickling filtration of biogas with high H 2 S. Assessment of 600 d of operation covered the reactor start-up, the operation at neutral pH and the transition from neutral to acid pH. During the start-up period, operational parameters such as the aeration rate and the trickling liquid velocity were optimized. During the steady-state operation at neutral pH, the performance of the random packing material was investigated by reducing the gas contact time at both constant and increasing H 2 S loads. The random packing material showed similar elimination capacities and removal efficiencies in comparison with previous studies with a structured packing material, indicating that Pall rings are suitable for biogas desulfurization in biotrickling filters. The diversity of Eubacteria and the structure of the community were investigated before and after the pH transition using the bacterial tag-encoded FLX amplicon pyrosequencing. The pH transition to acid pH drastically reduced the microbial diversity and produced a progressive specialization of the sulfur-oxidizing bacteria community without any detrimental effect on the overall desulfurizing capacity of the reactor. During acidic pH operation, a persistent accumulation of elemental sulfur was found.