Performance of a fungal monolith bioreactor for the removal of styrene from polluted air

Abstract

Gas-phase styrene removal using the fungus, Sporothrix variecibatus was evaluated in a novel monolith bioreactor, receiving a continuous supply of nutrients from the trickling liquid phase. During the start-up process, the monolith reactor was operated for 22 days with relatively low styrene concentrations in the gas-phase (<0.4 g m−3). Afterwards, continuous experiments were carried out at different inlet styrene concentrations, ranging between 0.06 and 2.5 g m−3, and at two different flow rates corresponding to empty bed residence times (EBRTs) of 77 and 19 s, respectively. A maximum elimination capacity of 67.4 g m−3 h−1 was observed at an inlet styrene load of 73.5 g m−3 h−1. However, it was observed that the critical loading rates to the monolith bioreactor were a strong function of the gas residence time. The critical load, with greater than 95% styrene removal was 74 g m−3 h−1 at an EBRT of 77 s, while it was only 37.2 g m−3 h−1 for an EBRT of 19 s. After 92 days of continuous operation, due to excess biomass growth on the surface of the monolith, the biodegradation efficiency decreased significantly. To ascertain the instantaneous response of the attached fungus, to withstand fluctuations in loading conditions, two dynamic shock loads were conducted, at EBRTs of 77 and 19 s, respectively. It was observed that, the performance of the monolith bioreactor decreased significantly at low residence times, when subjected to high shock loads. The recovery times for high performance, in both cases, did not exceed more than 1 h.