Comparative evaluation of a biotrickling filter and a tubular photobioreactor for the continuous abatement of toluene

Abstract The negative effects of volatile organic compounds (VOCs) on humans’ health and the environment have boosted the enforcement of regulations, resulting in the need of effective and environmentally friendly off-gas treatment technologies. In this work, the synergism between microalgae and bacteria was investigated as a sustainable platform to enhance the biological degradation of toluene, herein selected as a model VOC. An innovative algal-bacterial tubular photobioreactor (TPBR) was systematically compared with a conventional biotrickling filter (BTF). The BTF supported average removal efficiencies close to those obtained in the TPBR (86 ± 9% and 88 ± 4%, respectively) at the highest inlet load (∼23 g m 3  h −1 ) and lowest gas residence time (0.75 min). However, the BTF was more sensitive towards the accumulation of secondary metabolites. In this regard, photosynthetic O 2 supplementation (resulting in dissolved oxygen concentrations of ∼7.3 mg O 2 L −1 ) and CO 2 consumption by microalgae (which reduced the impact of acidification) enhanced toluene abatement performance and process stability.