Effect of loading types on performance characteristics of a trickle-bed bioreactor and biofilter during styrene/acetone vapor biofiltration

Abstract

A 2:1 (w/w) mixture of styrene (STY) and acetone (AC) was subjected to lab-scale biofiltration under varied loading in both a trickle bed reactor (TBR) and biofilter (BF) to investigate substrate interactions and determine the limits of biofiltration efficiency of typical binary air pollutant mixtures containing both hydrophobic and polar components. A comparison of the STY/AC mixture degradation in the TBR and BF revealed higher pollutant removal efficiencies and degradation rates in the TBR, with the pollutant concentrations increasing up to the overloading limit. The maximum styrene degradation rates were 12 and 8 gc m(-3) h(-1) for the TBR and BF, respectively. However, the order of performance switched in favor of the BF when the loading was conducted by increasing air flow rate while keeping the inlet styrene concentration (Cin) constant in contrast to loading by increasing Cin. This switch may be due to a drastic difference in the effective surface area between these two reactors, so the biofilter becomes the reactor of choice when the rate-limiting step switches from biochemical processes to mass transfer by changing the loading mode. The presence of acetone in the mixture decreased the efficiency of styrene degradation and its degradation rate at high loadings. When the overloading was lifted by lowering the pollutant inlet concentrations, short-term back-stripping of both substrates in both reactors into the outlet air was observed, with a subsequent gradual recovery taking several hours and days in the BF and TBR, respectively. Removal of excess biomass from the TBR significantly improved the reactor performance. Identification of the cultivable strains, which was performed on Day 763 of continuous operation, showed the presence of 7 G(-) bacteria, 2 G(+) bacteria and 4 fungi. Flies and larvae of Lycoriella nigripes survived half a year of the biofilter operation by feeding on the biofilm resulting in the maintenance of a nearly constant pressure drop.

Biofiltration of high concentrations of methanol vapors: removal performance, carbon balance and microbial and fly populations

“…A fly invasion ( Telmatoscopus albipunctatus ) was observed in a biofilter treating toluene . Recently, flies and larvae of Lycoriella nigripes were detected during half a year in a biofilter, feeding on biofilm and preventing excessive pressure drop . In another study, fly larvae appeared six weeks after inoculation.…”

“…42 Recently, flies and larvae of Lycoriella nigripes were detected during half a year in a biofilter, feeding on biofilm and preventing excessive pressure drop. 43 In another study, fly larvae appeared six weeks after inoculation. Such larvae were assumed to prevent biomass excess and to recycle nutrients.…”

Performance and feasibility of biotrickling filtration in the control of styrene industrial air emissions

“…Biotrickling filter (BTF), with an aqueous stream trickling through an inert packing material, provides advantages in comparison with conventional biofilter (BF) such as higher removal rates, lower energy consumption and smaller footprint requirements (Pérez et al, 2015). In this sense, Halecky et al (2016) compared the performance of a BTF packed with Pall rings and a BF packed with Poraver media during the treatment of vapors polluted with a 2:1 (wt:wt) mixture of styrene and acetone. BTF showed higher removal efficiencies (REs) with a maximum styrene elimination capacity (EC) of 13 g m -3 h -1 in comparison with 8.7 g m -3 h -1 of EC for the BF.…”

The botanical biofiltration of VOCs with active airflow: is removal efficiency related to chemical properties?

“…The current findings offer promising development opportunities for biofilter system optimisation, with the importance of VOC dipole moment suggesting that methods that promote both 12 dissolution into the aqueous phase and adsorption to substrate particles being likely means of improving VOC SPRE. VOC removal is a stepwise process: VOCs must firstly solubilise into the water phase in biofilter systems before they can undergo substrate adsorption or microbial degradation (Halecky et al, 2016). Without these effects, dissolved VOCs will leave the water phase with continual VOC loading once the water reaches the VOC saturation point (as per its Henry's law constant).…”