Transient-state operation of an anoxic biotrickling filter for H2S removal

The application of an anoxic biotrickling filter (BTF) for H2S removal from contaminated gas streams is a promising technology for simultaneous H2S and NO3- removal. Three transient-state conditions, i.e. different liquid flow rates, wet-dry bed operations and H2S shock loads, were applied to a laboratory-scale anoxic BTF. In addition, bioaugmentation of the BTF with a H2S removing-strain, Paracoccus MAL 1HM19, to enhance the biomass stability was investigated. Liquid flow rates (120, 60 and 30 L d(-1)) affected the pH and NO3- removal efficiency (RE) in the liquid phase. Wet-dry bed operations at 2-2 h and 24-24 h reduced the H2S elimination capacity (EC) by 60-80%, while the operations at 1-1 h and 12-12 h had a lower effect on the BTF performance. When the BTF was subjected to H2S shock loads by instantly increasing the gas flow rate (from 60 to 200 L h(-1)) and H2S inlet concentration (from 112 (+/- 15) to 947 (+/- 151) ppm(v)), the BTF still showed a good H2S RE (> 93%, EC of 37.8 g S m(-3) h(-1)). Bioaugmentation with Paracoccus MAL 1HM19 enhanced the oxidation of the accumulated S to sulfate in the anoxic BTF.