In this work, bioactive coating-based bioreactors have been applied to the treatment of three odorous indoor air pollutants (i.e., toluene, a-pinene, n-hexane), which are volatile organic compounds (VOC) of different hydrophobicities. The removal efficiency (RE) was evaluated at different empty bed residence times (EBRT) and inlet concentrations. The setup consisted of three bioreactors (namely BR 1, BR 2 and BR 3), packed with porous expanded clay. An enriched consortia of microorganisms was inoculated in BR 1 and BR 2, while fresh activated sludge was used in BR 3. A styrene-acrylate copolymer was employed for bioactive coating formulations in BR 2 and BR 3, while BR 1 performed as a conventional bioreactor.
BR 1 and BR 2 achieved REs over 90 % for toluene and a-pinene at an EBRT as low as 30 s. On the contrary, BR 3 only achieved REs >90 % when operated at an EBRT of 60 s, toluene and a-pinene removals decreasing to 67.0 % and 49.8 % at 30 s, respectively. The poorest performance was recorded at 15 s, with REs of toluene and a-pinene of 41.5% and 55.7% in BR 1, 44.3 % and 10.5 % in BR 2, and 22.2 % and 8.0 % in BR 3. n-hexane removal was poor and non-consistent. When decreasing inlet concentrations at EBRT 15 s, toluene and a-pinene REs progressively increased to reach 87.1% and 90.9 % in BR 1, 86.5 % and 76.6 % in BR 2, and 64.2 % and 70.6 % in BR 3. Overall n-hexane removal slightly increased but was still poorly reproducible.
Generally, no big differences were observed between the control and the bioactive coating bioreactor, suggesting that the bioactive coating can perform as good as conventional biofilm reactors. On the other hand, BR 3 performance was always inferior due to the lack of an adapted microbial community.