Center for Biofilm Engineering (CBE)
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/9334
At the Center for Biofilm Engineering (CBE), multidisciplinary research teams develop beneficial uses for microbial biofilms and find solutions to industrially relevant biofilm problems. The CBE was established at Montana State University, Bozeman, in 1990 as a National Science Foundation Engineering Research Center. As part of the MSU College of Engineering, the CBE gives students a chance to get a head start on their careers by working on research teams led by world-recognized leaders in the biofilm field.
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Item Biofouling and corrosion of stainless steels in natural waters(2002) Lewandowski, Zbigniew; Avci, Recep; Geiser, Michael Joseph; Braughton, K. R.; Yurt, NurdanThe noble shift in corrosion potential to values between +300 and +400 mVSCE and the accompanying increase in cathodic current density and polarization slope at mild cathodic potentials that develop during microbial colonization of passive metals, are collectively known as ennoblement. This phenomenon is of concern as the noble shift in the corrosion potential may lead to pitting corrosion. We have demonstrated, by growing pure cultures of manganese oxidizing bacteria (MOB) Leptothrix discophora SP-6 under well defined conditions, that microbial deposition of manganese oxides causes ennoblement of 316L stainless steel (SS). Exposing 316L corrosion coupons in lakes and streams supported this conclusion; the rate and extent of ennoblement were positively correlated with the rates of deposition and the amounts of biomineralized manganese oxides deposited on the surfaces of the SS corrosion coupons. X-ray photoelectron spectroscopy (XPS) analyses of the deposits from the ennobled coupons revealed a mixture of manganese oxides, as expected. Many natural waters can support growth of MOB. When manganese-oxidizing biofilms accumulate on surfaces of passive metals there is a potential for manganese redox cycling on the metal surface. This process is initiated by depositing minute amounts of manganese oxides on the metal surface. These microbially deposited manganese oxides are then reduced by the electrons derived from anodic dissolution of the metal; the metal is corroding and the manganese oxides are reduced to divalent manganese ions. However, since the manganese ions are liberated within the manganese-oxidizing biofilm, the manganese ions are immediately reoxidized, and the cycle continues.Item Manganese dioxide as a potential cathodic reactant in corrosion of stainless steels(2000) Olesen, Bo H.; Avci, Recep; Lewandowski, ZbigniewBiofilms of leptothrix discophora SP-6, grown on 316L stainless steel (SS), ennobled the open circuit potential to 410 mVSCE. X-ray Photoelectron Spectroscopy (XPS) identified MnO2 was studied using electroplated SS. Plated MnO2 was reduced amperometrically. The process was interrupted at different reduction stages. XPS analysis of remaining oxides showed that MnO2 was reduced through MnOOH to Mn2+. We conclude that biomineralized MnO2 may increase corrosion rates by serving as a cathodic reactant.Item Membrane fouling due to dynamic particle size changes in the aerated hybrid PAC–MF system(2011-04) Khan, Mohiuddin M. T.; Takizawa, S.; Lewandowski, Zbigniew; Jones, Warren L.; Camper, Anne K.; Katayama, H.; Ohgaki, S.To quantify the effect of dynamic particle size changes and degradation and accumulation of suspended solids (SS) in influents to reactors on membrane fouling frequency in hybrid powder-activated carbon (PAC)–microfiltration (MF) reactors, we operated a PAC–MF system (hollow-fiber module) for more than five months to purify river water before and after pretreatment by a biofilter. The transmembrane pressure, backwashing pressure, resistance to filtration, and SS accumulation and degradation during these dynamic changes were evaluated. The initial dose of PAC was 40 g/L of the reactor and no additional PAC was added during this continuous operational period. The presence of PAC reduced the membrane resistance to filtration even at the end of filtration period when the number of particles in the smallest range (>1.0–3.6 μm) was the highest measured by the flow cytometer and microscopy image analysis. This resistance was reduced further when the river water was biofiltered prior to membrane filtration. This real-time study demonstrates that over time PAC and other particles coming into the reactors through the influents degrade and/or become smaller because of the turbulence caused by continuous aeration below the MF membrane fibers. The number of particles in the reactors with diameters less than 10 μm increased with time, increasing the fouling frequency; however, the presence of PAC further reduced the particle enhanced fouling. The presence of PAC also increased SS degradation by up to 10%. The increased number of bacteria inside the PAC–MF systems did not contribute to the number of membrane fouling. Even though the particle sizes inside the reactors became smaller with time, the gradual increase in net accumulation of SS was also an important factor controlling the performance of the PAC–MF system.