Spontaneous granulation of hydrogen-producing bacteria can occur with shortened HRT in CSTR ( Fang et al., 2002a Oh et al., 2004b Yu and Mu, 2006). The highest hydrogen production rate of CSTR culture fermenting sucrose with a mixed hydrogen-producing microflora was reported as 1.12 liter/liter Hydrogen production rates are thus restricted considerably by a low CSTR biomass retention and low hydraulic loading ( Lay et al., 1999 Yu et al., 2002). Biomass washout is likely at short HRTs, resulting in deterioration in hydrogen production rates. Depending on the operating HRT, biomass inventory in a range between 1 and 4 g-VSS/liter is commonly reported ( Chen and Lin, 2003 Horiuchi et al., 2002 Lin and Chang, 1999 Zhang et al., 2006b).
Because of its intrinsic structure and operating pattern, a CSTR is unable to maintain high levels of biomass inventory. Compared with batch reactor systems, hydrogen-producing bacteria in a CSTR are well suspended in mixed liquor and suffer less from mass transfer resistance. Kuan-Yeow Show, Duu-Jong Lee, in Biohydrogen, 2013 Continuous ProcessesĬontinuous stirred tank reactors (CSTRs) are used frequently for continuous hydrogen production ( Chen and Lin, 2003 Majizat et al., 1997 Yu et al., 2002). On the contrary, membrane fouling and excessive operating cost may restrict the application of AMBR in hydrogen production. Other than enhancement in cells concentration, there is no apparent merit of AMBR over other biohydrogen systems. Hydrogen production rates ranging between 0.25 and 0.69 L/L∙h in AMBR systems were reported. Prolonging SRT can increase biomass inventory favoring substrate utilization, but may adversely lead to a decrease in hydrogen production rate. This was realized by maintaining sludge retention time (SRT) at 12 h, in line with a marginal rise in hydrogen production rate from 0.50 to 0.64 L/L∙h. It was shown that biomass inventory was increased from 2.2 g/L in a control unit (without membrane coupling) to 5.8 g/L in an anaerobic membrane bioreactor (AMBR) at 3.3 h HRT. Ī membrane-coupling reactor was employed to enhance biomass growth. In another study, it was reported that granular sludge disintegrated in less than 21 days when CSTRs were operated in static condition instead of agitated mode. With such cells inventory, the CSTR can be operated at higher OLRs (up to 20 g-glucose/L∙h) along with enhanced hydrogen production. found that granulation of sludge markedly increased the cells inventory to 16.0 g-VSS/L. Granulation of hydrogen-producing microbes can occur spontaneously with reduced HRT in CSTR. The highest production rate of CSTR fed with sucrose with mixed microflora was reported at 1.12 L/L∙h. The production rates were marked restricted by a weak CSTR cell retention and low hydraulic loading. Washout of cells could occur at short HRTs resulting in impeded hydrogen production. Depending on the HRT, cells concentration between 1 and 4 g-VSS/L is commonly recorded.
Attributable to its intrinsic reactor construction and completely mixed operation, a CSTR is incapable of maintaining high levels of cells inventory. In comparison with batch reactors, microbial cultures in a CSTR are evenly suspended in the liquor with lower resistance in mass transfer. Duu-Jong Lee, in Biohydrogen (Second Edition), 2019 4.2 Continuous ProcessesĬontinuous stirred tank reactors (CSTRs) are frequently investigated in continuous hydrogen production.