Downstream bioprocessing of CS2-polluted emissions: innovative use of a black slag in mixed biofilters

Black slag from an electric arc furnace (EAF) was used as an innovative inorganic co-packing material in organic biofilters for the biodegradation of CS2-polluted gases. The effect on biofilter performance of increasing the inlet concentration (IC) and reducing the empty bed residence time (EBRT) was evaluated in three biofilters packed with different bed configurations. Macrokinetic modelling pointed to a lower CS2 biodegradation activity related to the presence of the slag. Nevertheless, the presence of black slag improved long-term biofilter performance, and the maximum elimination capacity (43 g m−3 h−1) was recorded in the biofilter packed with a mixed support. Molecular profiling of the eubacterial populations demonstrated the ubiquitous presence of the potential CS2 degrading species Thiomonas intermedia. Co-packing with EAF slag also prompted the development of a more complex microbial community encompassing halophilic species involved in the metabolism of sulphur compounds (i.e. Thiohalophilus spp. and Paracoccus thiocyanatus).