Sludge/biofilm reactors

Table 1 reports a wide spectrum of typologies of biofilm reactor upflow anaerobic sludge bed (UASB), fluidized bed, airlift, fixed bed with and without recycle, mechanically agitated vessel, rotating drum and rotating biological contactor. Each reactor is characterized by positive features and drawbacks. 

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.)...

The other biofilm systems such as the rotating biological contactor (RBC) and the aerobic upflow sludge bed reactor (AUSB) shown in Fig. 2 could possibly be applied for MTBE removal, and may posses some unique advantages. However, to our knowledge these reactors have never been appHed for MTBE removal so far. 

Von Sperling, M. (2Q01) Activated Sludge and Aerobic Biofilm Reactors Biological Wastewater Treatment, vol. 5, IWA Publishing, London, p. 340. 

As stated earlier, the biodegradation of azo dyes requires an anaerobic and aerobic phase for the complete mineralization. The required condition can be implemented either by spatial separation of the two sludge using a sequential anaerobic-aerobic reactor system or in one reactor in the so-called integrated anaerobic-aerobic reactor system. In recent years, combined anaerobic-aerobic treatment technologies are extensively applied in the treatment of azo dye-containing wastewaters. Table 1 lists the systems based on combined anaerobic-aerobic treatment in separate reactors. Table 2 lists SBR based on temporal separation of the anaerobic and the aerobic phase. Table 3 lists the other systems, either hybrids with aerated zones or micro-aerobic systems based on the principle of limited oxygen diffuse in microbial biofilms [91]. 

The main reason for the popularity of the three widely used reactors lies in their ability to effectively retain a very high biomass concentration in their biofilms with a high sludge age and short hydraulic retention time. 

The main reactor types are upflow sludge blankets, biofilm fluidized beds, expanded granular sludge blankets, and biofihn airlift suspension and internal circulation reactors. 

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