Biofilm tank reactor

List of abbreviations BOD, biological oxygen demand CA, chloroanisol CCA, copper-chromate-arsenate CP, chlorophenol 2,4-D, dichlorophenoxyacetic acid DCP, dichlorophenol CFSTR, continuous-flow stirred tank reactor FBBR, fluidized-bed biofilm reactor MCP, monochlorophenol NAPL, non-aqueous phase liquid PAH, polycyclic aromatic hydrocarbon PCPP, polychlorinated phenoxyphenol PCDF, polychlorinated dibenzofuran PCDD, polychlorinated dibenzodioxin PCR, polymerase chain reaction PCP, pentachlorophenol PCA, pentachloroanisole TeCP, tetrachlorophenol TeCA, tetrachloroanisole TCC, trichlorocatechol TCP, trichlorophenol TOC, total organic carbon 2,4,5-T, trichlorophenoxyacetic acid UASB, upflow anaerobic sludge blanket reactor VSS, volatile suspended solids. 

FBBR, fluidized-bed biofilm reactor CFSTR, completely mixed stirred tank reactor PUR, polyurethane immobilized cells UASB, upflow anaerobic sludge blanket reactor NS, not specified. 

Fig. 1 Bioreactors. (A) activated sludge reactor (B) stirred tank reactor and (C) rotating biofilm reactor. (View this art in color at www.dekker.com.)...

Figure 1. Continuous tank reactor with biofilm.

In an analysis of the near initial rate of biofilm accumulation Bryers and Characklis [1981] related the development of biofilm to the concept of a continuous stirred tank reactor. They took into account the effects of shear forces and associated removal of biofilm and assumed that the subsequent effects were dependent on the biofilm already on the surface, i.e. 

Reid, D.C., Bott, T.R. and Miller, R., 1992, Biofouling in stirred tank reactors -effect of surface finish, in Melo, L.F., Bott, T.R., Fletcher, M. and Capdeville, B. eds. Biofilms - Science and Technology, 521 - 526, Kluwer Academic Publishers, Dordrecht. 

In this example, a fluidised biofilm sand bed reactor for nitrification, as investigated by Tanaka et al. (1981), is modelled as three tanks-in-series with a recycle loop (Fig. 1). With continuous operation, ammonium ion is fed to the reactor, and the products nitrite and nitrate exit in the effluent. The bed expands in volume because of the constant circulation flow of liquid upwards through the bed. Oxygen is supplied external to the bed in a well-mixed gas-liquid absorber. 

The model balance equations are developed by considering both the individual tank stages and the absorber. Component balances are required for all components in each section of the reactor column and in the absorber, where the feed and effluent streams are located. Although the reaction actually proceeds in the biofilm phase, a homogeneous model apparent kinetics model is employed, which is justified by its simplicity. 

Industrial hazardous wastewater can be treated aerobically in suspended biomass stirred-tank bioreactors, plug-flow bioreactors, rotating-disc contactors, packed-bed fixed-biofilm reactors (or biofilters), fluidized bed reactors, diffused aeration tanks, airlift bioreactors, jet bioreactors, membrane bioreactors, and upflow bed reactors [28,30]. 

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