Aerobic biofilms were found to have a complex structure consisting of microbial cell clusters (discrete aggregates of densely packed cells) and interstitial voids. The oxygen distribution was strongly correlated with these strutures. The voids facilitated oxygen transport from the bulk liquid through the biofilm, supplying approximately 50% of the total oxygen consumed by the cells. The mass transport rate from the bulk liquid is influenced by the biofilm structure; the observed exchange surface of the biofilm is twice that calculated for a simple planar geometry. The oxygen diffusion occurred in the direction normal to the cluster surfaces, the horizontal and vertical components of the oxygen gradients were of equal importance. Consequently, for calculations of mass transfer rates a three-dimensional model is necessary. These findings imply that to accurately describe biofilm activity, the relation between the arrangement of structural components and mass transfer must be undrstood. (c) 1994 John Wiley & Sons, Inc.

Effects of biofilm structures on oxygen distribution and mass transport.

Bioreactors for treatment of VOCs and odours - a review.

Bacterial dehalogenases: biochemistry, genetics, and biotechnological applications.

This article describes the use of biofilm reactors for the production of various chemicals by fermentation and wastewater treatment. Biofilm formation is a natural process where microbial cells attach to the support (adsorbent) or form flocs/aggregates (also called granules) without use of chemicals and form thick layers of cells known as "biofilms." As a result of biofilm formation, cell densities in the reactor increase and cell concentrations as high as 74 gL-1 can be achieved. The reactor configurations can be as simple as a batch reactor, continuous stirred tank reactor (CSTR), packed bed reactor (PBR), fluidized bed reactor (FBR), airlift reactor (ALR), upflow anaerobic sludge blanket (UASB) reactor, or any other suitable configuration. In UASB granular biofilm particles are used. This article demonstrates that reactor productivities in these reactors have been superior to any other reactor types. This article describes production of ethanol, butanol, lactic acid, acetic acid/vinegar, succinic acid, and fumaric acid in addition to wastewater treatment in the biofilm reactors. As the title suggests, biofilm reactors have high potential to be employed in biotechnology/bioconversion industry for viable economic reasons. In this article, various reactor types have been compared for the above bioconversion processes.

/pdf/biofilm-reactors-for-industrial-bioconversion-processes-3mz74ovyp6.pdf

Biofilm reactors for industrial bioconversion processes: employing potential of enhanced reaction rates

In this paper we present a review of the existing air pollution control technologies (APCT), when used essentially for the elimination of volatile organic compounds (VOC). The biotechnologies referred to, bioscrubbers, biotrickling filters and biofilters, are also described. A more detailed review of biofiltration is proposed, presenting the most recent and latest developments achieved in the field of bioprocessing. In particular, the influence of the filter bed, the polluted air flowrates, the pollutants, the pressure drop, bed moisture content, temperature, nutrients, pH and the microorganisms are reviewed. Models of biofiltration are also presented.

Biofiltration of air: a review.

Exhaust Gas Purification

Biofiltration is a technique which is frequently applied for the odour abatement of waste gases. This technique is based on the ability of microorganisms (generally bacteria, and to a small extent moulds and yeasts) to degrade several organic as well as inorganic compounds to mineral end-products, like water and carbon dioxide. In the case of biofiltration, microorganisms are attached to suited packing materials in the filter, which contain the inorganic nutrients necessary for microbial growth. In order to make biofiltration applicable on a larger scale in process industry, it is necessary to find microorganisms able to eliminate compounds which are strange to life, the so-called xenobiotics. At the Eindhoven University of Technology microorganisms were isolated for the elimination of a number of xenobiotics, e.g. aromatic compounds and chlorinated hydrocarbons.

Biological elimination of volatile xenobiotic compounds in biofilters

https://pure.tue.nl/ws/files/2165948/620777.pdf

Biological systems for waste gas elimination

Biological purification of waste gases

Publisher Summary This chapter discusses process technology of biotechniques. The number of applications of biological treatment systems for off-gas purification has strongly increased. The application of a biological treatment system is based upon the microbial degradability of the compounds present in the waste gas. The performance of a continuously operating bioreactor is the ultimate result of a complex interaction between the microbiological and physical phenomena, called as the “macrokinetics” of the process. The microkinetics of the degradation process are generally investigated and modeled for pure cultures of suspended microorganism. In many bioreactor systems the degradation also takes place within fixed biofilms, which means that additional mass transfer phenomena (i.e., mass transfer to the biofilm and internal diffusion) should be taken into account. The elimination of organic substrates by microorganism results from the fact that those organisms can use the organic compounds as its sole energy—catabolism, and carbon source—anabolism.

S.P.P. Ottengraf

Papers

Exhaust Gas Purification

Biological elimination of volatile xenobiotic compounds in biofilters

Biological systems for waste gas elimination

Biological purification of waste gases

Process Technology of Biotechniques