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The Membrane Biofilm Reactor Is A Versatile Platform For Water And Wastewater Treatment
Bruce E. Rittmann 대한환경공학회 2007 Environmental Engineering Research Vol.12 No.4
The membrane biofilm reactor (MBfR) creates a natural partnership of a membrane and biofilm, because a gas-transfer membrane delivers a gaseous substrate to the biofilm that grows on the membrane`s outer wall. O₂-based MBfRs (called membrane aerated biofilm reactors, or MABRs) have existed for much longer than H₂-based MBfRs, but the H₂-based MBfR is a versatile platform for reducing oxidized contaminants in many water-treatment settings: drinking water, ground water, wastewater, and agricultural drainage. Extensive bench-scale experimentation has proven that the H₂-based MBfR can reduce many oxidized contaminant to harmless or easily removed forms: e.g., NO₃- to N2, ClO₄- to H₂O and Cl-, SeO₄2- to Se°, and trichloroethene (TCE) to ethene and Cl-. The MBfR has been tested at the pilot scale for NO₃- and ClO₄- and is now entering field-testing for many of the oxidized contaminants alone or in mixtures. For the MBfR to attain its full promise, several issues must be addressed by bench and field research: understanding interactions with mixtures of oxidized contaminants, treating waters with a high TDS concentration, developing modules that can be used in situ to augment pre-denitrification of wastewater, and keeping the capital costs low.
Life-cycle kinetic model for endospore-forming bacteria, including germination and sporulation
Park, Seongjun,Rittmann, Bruce E.,Bae, Wookeun Wiley Subscription Services, Inc., A Wiley Company 2009 Biotechnology and Bioengineering Vol.104 No.5
<P>We develop a mechanistic life-cycle model for endospore-forming bacteria (EFB) and test the model with experiments with a Bacillus mixed culture. The model integrates and quantifies how sporulation and germination are triggered by depletion or presence of a limiting substrate, while both substrates affect the rate of vegetative growth by a multiplicative model. Kinetic experiments show the accumulation of small spherical spores after the triggering substrate is depleted, substantially more rapid decay during sporulation than for normal decay of vegetative cells, and a higher specific substrate utilization rate for the germinating cells than that for growth of vegetative cells. Model simulations capture all of these experimental trends. According to model predictions, when a batch reactor is started, seeding with EFB spores instead of active EFB delays the onset of rapid chemical oxygen demand (COD) utilization and biomass growth, but the end points are the same. Simulated results with low aeration intensity show that germination can consume some substrate without dissolved oxygen (DO) depletion. Biotechnol. Bioeng. 2009; 104: 1012–1024. © 2009 Wiley Periodicals, Inc.</P>
Park, Seongjun,Bae, Wookeun,Rittmann, Bruce E. Wiley Subscription Services, Inc., A Wiley Company 2010 Biotechnology and Bioengineering Vol.105 No.6
<P>A multi-species nitrifying biofilm model (MSNBM) is developed to describe nitrite accumulation by simultaneous free ammonia (FA) and free nitrous acid (FNA) inhibition, direct pH inhibition, and oxygen limitation in a biofilm. The MSNBM addresses the spatial gradient of pH with biofilm depth and how it induces changes of FA and FNA speciation and inhibition. Simulations using the MSNBM in a completely mixed biofilm reactor show that influent total ammonia nitrogen (TAN) concentration, bulk dissolved oxygen (DO) concentration, and buffer concentration exert significant control on the suppression of nitrite-oxidizing bacteria (NOB) and shortcut biological nitrogen removal (SBNR), but the pH in the bulk liquid has a weaker influence. Ammonium oxidation increases the nitrite concentration and decreases the pH, which together can increase FNA inhibition of NOB in the biofilm. Thus, a low buffer concentration can accentuate SBNR. DO and influent TAN concentrations are efficient means to enhance DO limitation, which affects NOB more than ammonia-oxidizing bacteria (AOB) inside the biofilm. With high influent TAN concentration, FA inhibition is dominant at an early phase, but finally DO limitation becomes more important as TAN degradation and biofilm growth proceed. MSNBM results indicate that oxygen depletion and FNA inhibition throughout the biofilm continuously suppress the growth of NOB, which helps achieve SBNR with a lower TAN concentration than in systems without concentration gradients. Biotechnol. Bioeng. 2010;105: 1115–1130. © 2009 Wiley Periodicals, Inc.</P>
Effects of Electron Acceptor and Electron Donor on Biodegradation of CCl₄ by Biofilms
Bae, Woo Keun,Bruce E. Rittmann 한국환경독성학회 1991 환경독성보건학회지 Vol.6 No.2
Biodegradation of carbon tetrachloride (CTC) in denitrifying and aerobic columns was investigated under various conditions of electron-acceptor and electron-donor availability. CTC removal increased when the electron-acceptor (nitrate) injection was stopped in the denitrifying column; however, CTC removal decreased when electron donor (acetate) was deleted in the denitrifying and the aerobic column. Small fractions of the CTC removed appeared as chloroform, indicating that reductive dechlorination of CTC was occurring. The results from the denitrifying column support the hypothesis that CTC behaves as an electron acceptor that competes for the pool of available electrons inside the bacterial cells.