Integration of a nitrification bioreactor and an anoxic biotrickling filter for simultaneous ammonium-rich water treatment and biogas desulfurization

Abstract

A preliminary assessment has been carried out on the integration of an anoxic biotrickling filter and a nitrification bioreactor for the simultaneous treatment of ammonium-rich water and H2S contained in a biogas stream. The nutrient consumption in the biotrickling filter was as follows (mol−1 NO3−-N): 6.3·10−4 ± 1.2·10−4 mol PO43−-P, 0.04 ± 0.05 mol NH4+-N and 0.04 ± 0.03 mol K+-K. Furthermore, it was possible to supply a mixture of biogenic NO3− and NO2− into the biotrickling filter from the nitrification bioreactor to obtain a maximum elimination capacity of 152 gH2S–S m−3 h−1. The equivalence between the two compounds was 1 mol NO3−-N equal to 1.6 mol NO2−-N. The biotrickling filter was also operated under a stepped variable inlet load (30–100 gH2S–S m−3 h−1) and outlet H2S concentrations of less than 150 ppmV were obtained. It was also possible to maintain the outlet H2S concentration close to 15 ppmV with a feedback controller by manipulating the feed flow (in the nitrification bioreactor). Two stepped variable inlet loads were tested (60–111 and 16–102 gH2S–S m−3 h−1) under this type of control. The implementation of feedback control could enable the exploitation of biogas in a fuel cell, since the H2S concentrations were 15.1 ± 4.3 and 15.0 ± 3.4 ppmV. Finally, the anoxic biotrickling filter experienced partial denitrification and this implied a loss of the desulfurization effectiveness related to SO42− production.