Novel membrane bioreactor: Able to cope with fluctuating loads, poorly water soluble VOCs, and biomass accumulation

Abstract

Biological waste gas treatment is an attractive method for controlling air emissions of volatile organic compounds (VOCs). Microorganisms degrade the VOCs to harmless products such as carbon dioxide (CO(2)), biomass and water. In spite of the advantages, significant unresolved challenges remain for biological waste gas treatment. Fluctuating loads in waste gas streams, especially of VOCs with low water solubility, can often not be satisfactorily removed. Concentration peaks leave the reactor virtually untreated, while periods without VOCs in the waste gas lead to starvation of the bacteria. Furthermore, bioreactors are often subject to clogging due to biomass accumulation. In the current work, a flat sheet membrane bioreactor was developed which was able to buffer fluctuating loads of toluene, our model compound, by absorption in silicone oil prior to degradation and which continuously removed and discharged excess biomass from the reactor. The absorption and the biodegradation were both membrane based. An inverse bacterial biofilm developed on the membrane, which separated the culture medium from the absorbent. The culture medium was constantly passed along the biofilm, introducing shear stresses on the surface and thereby removing excess, inactive biomass. The toluene surface elimination capacity was virtually independent of the gas flow rate for the tested steady-state conditions and reached a maximum of 0.6 g m(-2) h(-1). Experiments with fluctuating inlet mass flow rates of toluene confirmed the excellent buffering capability of the set-up. The reactor was successfully operated for 162 days without clogging.

A state–of–the-art review on indoor air pollution and strategies for indoor air pollution control

“…Secondly, the risk of an undesired stripping of microorganisms is avoided and the excess of humidity in the purified air is limited. Finally, the mass-transfer of gas pollutants is improved due to the affinity and permeability of the membrane, especially in the case of hydrophobic pollutants (Kumar et al, 2008;Studer and von Rohr, 2008). Membrane bioreactors have been tested for the treatment of high VOC concentration, and their performance in indoor air applications remains unexplored.…”

A two‐phase partitioning airlift bioreactor for the treatment of BTEX contaminated gases

“…However, biofilters can have limitations such as bed drying, biomass clogging, and the inability to effectively handle fluctuations in loading (Khan and Ghoshal, 2000). Therefore, there has been recent interest in the design and improvement of novel biological BTEX treatment systems that have the ability to operate beyond the current abilities of biofilters (Kan and Deshusses, 2005;Studer and von Rohr, 2008). However, design of novel biological treatment systems can often involve stirred tank reactors, which are energy intensive and compromise the energy benefits that are typically associated with biological treatment methods.…”

Elimination of NH3 and odor from composting by biotrickling filter and preliminary exploration on molecular biology

“…Therefore, it might be assumed that biological process can not fully eliminate the organic compounds. Because principle of biological VOCs treatment is that microorganisms degrade the VOCs to harmless products such as carbon dioxide (CO2), biomass and water (Studer & von Rohr 2008), this finding should be a significant concern for researchers and designers of biological process for treatment of VOCs. The similar case, some VOCs being produced as by-products of microbial oxidation, was found in biofilters (Nicolai & Janni 2001), In addition, removal efficiency of the other VOCs was 35.3% on average calculated from the sum of peak areas.…”