Styrene removal in a biotrickling filter and a combined UV–biotrickling filter: Steady- and transient-state performance and microbial analysis

Abstract A laboratory-scale combined UV photodegradation and biotrickling filter (UV–BTF) system as well as a single biotrickling filter (BTF) were evaluated for removal of gaseous styrene. Empty bed residence time (EBRT) and inlet styrene concentrations were 30–70 s and 0.5–4.0 g m −3 . A maximum elimination capacity (EC max ) of 309 g m −3  h −1 was achieved by the combined UV–BTF at an inlet loading rate (ILR) of 476 g m −3  h −1 with a removal efficiency (RE) of 65%. The better performance of BTF was due to the UV photodegradation that converted styrene into compounds that were more easily degraded (benzoate, phenol, isopropyl alcohol, etc.) for subsequent biological treatment. Bacterial community analysis revealed that abundant bacteria including Proteobacteria (α-, β-, γ- and δ-), Actinobacteria and Firmicutes were responsible for styrene removal in the BTF and UV–BTF. When subjected to short (12 h) and long-term (180 h) shut-downs, the combined system still offered high EC values of 156 and 304 g m −3  h −1 , respectively, after resuming operation at 2 and 12 h, respectively. Intermittent shutdown (3 d) with nutrient addition and a 10 d shutdown without nutrient addition had no apparent effects on the combined biofilter. The results showed that the UV photodegradation had a positive effect on the subsequent BTF, and the combined system was stable under both steady and transient states.