Gas-phase bioreactor

Treatment of contaminated liquids such as water, leachate, filtrate, groimdwater, storm water, surface water and industrial process waste water can be accomplished by several of SBP s technologies. Certain waste streams can be concentrated by the hyperfiltration units the permeate is clean water and the "ctMicentrate" contains the reduced volume of the pollutants. These concentrated contaminants can often be bioremediated, thus minimizing the waste stream. Other liquids may be treated directly, either by biological processes, or in the case of volatiles, air stripping with biotreatment of the pollutants in a gas phase bioreactor, or "biofilter". 

R. Redondo, V.C. Machado, M. Baeza, J. Lafuente, D. Gabriel, On-line monitoring of gas-phase bioreactors for biogas treatment hydrogen sulfide and sulfide analysis by automated flow systems. Anal. Bioanal. Chem. 391 (2008) 789-798. 

Nagayama, K., Spiel , A.C., and Biichs, J. (2012) Enhanced catalytic performance of immobilized Parvibaculum lavamcntivorans alcohol dehydrogenase in a gas phase bioreactor using glycerol as an additive. Chem. Eng.]., 207-208, 342-348. 

In a stirred bioreactor the Hquid is generally considered weU-mixed, ie, is spatially constant. The gas phase too may be weU-mixed (19) so that... 

For large-scale bioreactors (21), especially those of the air lift type (22), the gas phase is best considered as being in plug dow, so that a log mean value of driving force is obtained ... 

The specific surface, a, is also relatively insensitive to the duid dynamics, especially in low viscosity broths. On the other hand, it is quite sensitive to the composition of the duid, especially to the presence of substances which inhibit coalescence. In the presence of coalescence inhibitors, the Sauter mean bubble size, is significantly smaller (24), and, especially in stirred bioreactors, bubbles very easily circulate with the broth. This leads to a large hold-up, ie, increased volume fraction of gas phase, 8. Sp, and a are all related... 

The typical bioreactor is a two-phase stirred tank. It is a three-phase stirred tank if the cells are counted as a separate phase, but they are usually lumped with the aqueous phase that contains the microbes, dissolved nutrients, and soluble products. The gas phase supplies oxygen and removes by-product CO2. The most common operating mode is batch with respect to biomass, batch or fed-batch with respect to nutrients, and fed-batch with respect to oxygen. Reactor aeration is discussed in Chapter 11. This present section concentrates on reaction models for the liquid phase. 

Frohlich, S., Lotz, M., Korte, T., Lilbbert, A., Schilgerl, K., Seekamp, M., Characterization of a Pilot Plant Airlift Tower Loop Bioreactor II. Evaluation of Global Mixing Properties of the Gas Phase During Yeast Cultivation, Biotechnol. Bioeng., 37 910 (1991a)... 

Reactor in a combination of a membrane bioreactor and a bubble-column and was designed for simultaneous degradation of both hydrophilic and hydrophobic contaminants from the gas phase. 

In a bioreactor, one is interested in the transfer per unit of volume of reactor, called Kia or the volumetric mass-transfer coefficient, a is the interfacial surface area per unit of volume of liquid. In a perfectly mixed tank, C has identical values at any point and C depends on the conditions in the gas phase at the outlet of the reactor. Several authors [60] consider that a better estimate of the driving force is given by the logarithmic mean concentration difference between the entry and the exit of gas. 

As most biochemical reactions occur in the liquid phase, bioreactors usually handle liquids. Processes in bioreactors often also involve a gas phase, as in cases of aerobic fermentors. Some bioreactors must handle particles, such as immobilized enzymes or cells, either suspended or fixed in a liquid phase. With regard to mass transfer, microbial or biological cells may be regarded as minute particles. 

The treatment of PAH-contaminated soil in a reactor environment is basically limited to the use of soil slurry reactors. Conversely, many different bioreactor designs exist for the treatment of water contaminated with PAHs. As reviewed by Grady (1989) and Grady Lim (1980), these include fixed film reactors, plug flow reactors, and a variety of gas-phase systems, to name a few. Given the depth and magnitude of such a topic, for the purposes of this review discussions will be limited to a generic overview of reactor applications for PAH bioremediation. 

The phases present in the bioreactor are (1) solid phase of particulates and biomass, (2) liquid phase of water and ethanol, with the reacting agents and nutrition for the biomass and (3) gas phase with the products of the reaction (N2, and C02). 

Three-phase fluidized beds can be used as bioreactors for aerobic biochemical processes, including both fermentation processes and wastewater treatment. The gas phase is air, required for biological growth, while the solid particles provide immobilized surfaces on or in which cell growth can occur. The aqueous liquid phase provides the culture medium needed for the growth and maintenance of the cells. Air may be introduced separately from the liquid, or be premixed with the aqueous medium. The liquid medium may exhibit non-Newtonian rheology. A disadvantage of three-phase... 

Gas-solid fluidized-bed bioreactors are actively used to perform solid-state fermentation [74,76]. The particular solid substrate is placed on a porous plate or metal net and sterilized air is blown in under the plate. When the air flow rate is high enough, solid substrate particles will be suspended in the gas phase. Advantages of the fluidized-bed bioreactor include ... 

---