Bioscrubbing of waste gas—substrate absorber to avoid instability induced by inhibition kinetics

Abstract

The stability of a continuous stirred tank bioreactor treating a gas stream containing monochlorobenzene (MCB) was studied theoretically and experimentally. A bioreactor inoculated with Pseudomonas sp. strain JS150 was submitted to successive step disturbances in the MCB load, inducing washout and system instability. With time, and subject to high MCB concentrations in the biomedium, the microorganisms appeared to adapt to high MCB load, and needed increasingly severe shocks to induce washout. To improve the bioreactor stability, the influence of an MCB-absorber prior to the bioreactor was investigated, using silicone oil as the absorbent for MCB. A parallel was established with the first set of experiments (no absorber). Phase plane plots showed how the presence of the absorber changed the system trajectories from washout into stable pseudo-steady states. Experimental results confirmed the benefits of the absorber in avoiding washout under high MCB loads. At periods of low loading, MCB was desorbed from the absorber. For the same loading conditions, removal efficiencies were much higher than when no absorber was present. Elimination capacities observed in the bioreactor were much higher than those previously reported for biotrickling filters treating MCB containing gas streams: 300 to 450 g m(-3) h(-1). Gas inlet concentrations were in the range 12 to 65 g m(-3), well above the 5 g m(-3) upper limit usually suggested for biological treatment of waste gases, showing that highly concentrated gas streams may be biologically treated so long as inhibitory concentrations are not reached in the bioreactor.

Bioprocesses for air pollution control

“…Thus, microorganisms in that water phase will not be inhibited. Conversely, in the presence of a single aqueous liquid phase high pollutants concentrations may lead to inhibitory conditions and biomass washout, 139 although the toxic effect may be somewhat less significant in such a completely mixed reactor than in packed bed biotrickling filters. 20 It was observed that under given operating conditions the biomass concentration in the reactor will naturally reach and stabilize at a rather constant value.…”

“…20,141 A similar effect will also be reached if an organic phase absorber is put in front of a conventional single aqueous phase stirred tank bioreactor, instead of directly mixing both the aqueous and the organic phase in the bioreactor itself. 139 Some typical examples of performance data for two-liquid phase stirred tank bioreactors are summarized in Table 6.…”

Novel membrane bioreactor: Able to cope with fluctuating loads, poorly water soluble VOCs, and biomass accumulation

“…Silicone oil has small gas-absorbent partition coefficients for toluene and for oxygen, it is miscible with toluene, and it features a high solubility for oxygen (De Bo et al, 2002;Poddar et al, 1996;Studer, 2005). Silicone oil has successfully been applied as an absorbent in biological waste gas treatment systems to control fluctuating concentrations of organics (Koutinas et al, 2006;Oliveira and Livingston, 2003).…”

“…The load fluctuations described above are challenging for biological waste gas treatment systems as they are sensitive to transient feed conditions and process shutdowns (Al Rayes et al, 2001;Choi et al, 1998;Cox and Deshusses, 2002;Koutinas et al, 2006;Oliveira and Livingston, 2003). Shortterm inlet fluctuations of VOCs can reduce the performance of a bioreactor by stressing the microorganisms (Al Rayes et al, 2001).…”

Evidence of species succession during chlorobenzene biodegradation

“…In particular, complete mineralisation of MCB and a series of other substituted benzenes has been described for Burkholderia strain JS150 (Haigler et al, 1992). This strain has been studied in several bioreactor configurations for the treatment of MCB contaminated streams (Ferreira Jorge and Livingston, 2000;Haigler et al, 1992;Oliveira and Livingston, 2003). However, the latest study reported its disappearance from a functionally stable bioreactor (Emanuelsson et al, 2005).…”