Progressive change from nitrate to nitrite as the electron acceptor for the oxidation of H2S under feedback control in an anoxic biotrickling filter

Nitrate has been progressively replaced by nitrite as the electron acceptor in the oxidation of H2S from biogas mimic by an anoxic biotrickling filter. Perturbations in the inlet H2S concentration with and without the implementation of feedback controllers have been evaluated. Nitrite was successfully used without decreasing the H2S removal efficiency (94.74 +/- 0.01%). Moreover, a PID controller allowed the sulfate selectivity to be maintained and reduced the maximum outlet H2S concentration when compared to the system without control (54.4-64.4%), although elemental sulfur was the main oxidation product. On using ORP control the main disadvantage was the production of peaks in the outlet H2S concentration. The stability and resilience of the biological system were assessed by analyzing the microbial community profiles by 16S rDNA-denaturing gradient gel electrophoresis (DDGE). The modification of the electron acceptor led to a reduction in the diversity and increased the dominance of the microbial populations.