Bioreactor slurry

Mixing tank Slurry Bioreactors Slurry Dewatering... 

Bioreactors. Biodegradation is carried out in a container or reactor it may be used to treat liquids or slurries. 

The slurry bioreactor developed by ECOVA Corporation65 showed a 93.4% reduction in PAHs over a 12-week treatment period with an initial 89.3% reduction in the first two weeks. 

A slurry bioreactor with an aqueous biocatalytic solution, containing the mineral nutrients and an assimilable source of carbon. 

A slurry bioreactor where carbonaceous feedstock is directly contacted with the biocatalyst. 

The 1980 s and the early 1990 s have seen the blossoming development of the biotechnology field. Three-phase fluidized bed bioreactors have become an essential element in the commercialization of processes to yield products and treat wastewater via biological mechanisms. Fluidized bed bioreactors have been applied in the areas of wastewater treatment, discussed previously, fermentation, and cell culture. The large scale application of three-phase fluidized bed or slurry bubble column fermen-tors are represented by ethanol production in a 10,000 liter fermentor (Samejima et al., 1984), penicillin production in a 200 liter fermentor (Endo et al., 1986), and the production of monoclonal antibodies in a 1,000 liter slurry bubble column bioreactor (Birch et al., 1985). Fan (1989) provides a complete review of biological applications of three-phase fluidized beds up to 1989. Part II of this chapter covers the recent developments in three-phase fluidized bed bioreactor technology. 

Figure 3. Autoradiographic detection of naphthalene degradative bacterial colonies from MGP soil enrichments used as inoculum for continuous stirred soil slurry bioreactors.

If all three technologies [soil washing (SW), slurry bioreactor (SBR), and BioTrol aqueous treatment system (BATS)] are used, the estimated cost of a commercial-scale soil washing system is 168/ton ( 185/metric ton). Incineration of woody material removed during washing accounts for 76% of the cost (D110690, p. 43). 

Molasses has been used in slurry-phase bioreactors to encourage the bioremediation of explosives. The costs of this ex situ system were calculated based on the pilot-scale demonstration at the Joliet Army Ammunition Plant in Joliet, Illinois. The projected costs of a full-scale remediation using the slurry-phase treatment system ranged from 290 to 350/yd (D210571, p. 67). 

The Biolift slurry bioreactor is an ex situ technology for the bioremediation of soil or sludges contaminated with organic hazardous wastes. Slurry-phase bioremediation, while more costly... 

Bubble columns in which gas is bubbled through suspensions of solid particles in liquids are known as slurry bubble columns . These are widely used as reactors for a variety of chemical reactions, and also as bioreactors with suspensions of microbial cells or particles of immobilized enzymes. 

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. 

Glaser, J.A., McCauley, P.T., Dosani, M. A., Platt, J.S. Krishan, E. R. (1994). Engineering optimization of slurry bioreactors for treating hazardous wastes. In Proceedings, Symposium on Bioremediation of Hazardous Wastes Research, Development and Field Evaluations, pp. 109-15. EPA/600/R-94/075. 

Stormo, K. E. Deobald, L. A. (1995). Novel slurry bioreactor with efficient operation and intermittent mixing capabilities. In Bioaugmentation for Site Remediation, ed. R. E. Hinchee, G. D. Sayles B.C. Alleman, pp. 129-35. Columbus, OH Battelle Press. 

Compeau et al. (1990) reported a full-scale slurry-phase PCP remediation. The system consisted of soil washing and screening and resulted in clean soil and wash solution. The wash solution was a slurry containing PCP and < 60-mesh-size soil particles at approximately 20% solids concentration. Slurry was treated subsequently in on-site slurry-phase bioreactors. A 50 m3 slurry reactor was operated in batch mode and inoculated by an uncharacterized PCP-mineralizing culture (107 cells/ml of slurry). After 14 days, 370mg PCP/kg slurry had been degraded to below 0.5 mg/kg. For effective biogradation to occur, inoculation was required. 

Slurry bioreactors offer the most aggressive approach to maximizing contact between the contaminated soil and the degrading organisms. Slurry bioreactors are usually the most expensive bioremediation option because of the large power requirements, but under some conditions this cost is offset by the rapid biodegradation that can occur. 

There is good heat transfer in agitated gas-liquid-solid slurry reactors see, e.g., van t Riet and Tramper for correlations (Basic Bioreactor Design, Marcel Dekker, 1991). 

General design considerations for mechanically agitated gas-liquid and gas-liquid-solid mechanically agitated reactors described earlier in Sections II and III are applicable here. In this section, however, we evaluate additional design considerations that are specific to bioreactors. Novel reactors to overcome specific needs of biological processes are also evaluated in this section. The characteristics of the bioreactors and other chemical/ petrochemical gas-liquid and slurry reactors are compared in Table XX. 

---