Browsing by Author "Jones, Warren L."

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Anaerobic srb biofilms in industrial water systems: a process analysis
(1993) Okabe, Satoshi; Jones, Warren L.; Lee, Whonchee; Characklis, William G.
Characterization of initial events in bacterial surface colonization by two pseudomonas species using image analysis
(1992-05) Mueller, Robert Franz; Characklis, William G.; Jones, Warren L.; Spears, J.
The processes leading to bacterial colonization on solidwater interfaces are adsorption, desorption, growth, and erosion. These processes have been measured individually in situ in a flowing system in real time using image analysis. Four different substrata (copper, silicon, 316 stainless-steel and glass) and 2 different bacterial species (Pseudomonas aeruginosa and Pseudomonas fluorescens) were used in the experiments. The flow was laminar (Re = 1.4) and the shear stress was kept constant during all experiments at 0.75 N m−2. The surface roughness varied among the substrata from 0.002 μm (for silicon) to 0.015 μm (for copper). Surface free energies varied from 25.1 dynes cm−1 for silicon to 31.2 dynes cm−1 for copper. Cell curface hydrophobicity, reported as hydrocarbon partitioning values, ranged from 0.67 for Ps. fluorescensto 0.97 for Ps. aeruginosa. The adsorption rate coefficient varried by as much as a factor of 10 among the combinations of bacterial strain and substratum material, and was positively correlated with surface free energy, the surface roughness of the substratum, and the hydrophobicity of the cells. The probability of desorption decreased with increasing surface free energy and surface roughness of the substratum. Cell growth was inhibited on copper, but replication of cells overlying an initial cell layer was observed with increased exposure time to the cell-containing bulk water. A mathematical model describing cell accumulation on a substratum is presented.
Chemical and antimicrobial treatments change the viscoelastic properties of bacterial biofilms
(2011-01) Jones, Warren L.; Sutton, Michael P.; McKittrick, Ladean R.; Stewart, Philip S.
Changes in the viscoelastic material properties of bacterial biofilms resulting from chemical and antimicrobial treatments were measured by rheometry. Colony biofilms of Staphylococcus epidermidis or a mucoid Pseudomonas aeruginosa were subjected to a classical creep test performed using a parallel plate rheometer. Data were fit to the 4-parameter Burger model to quantify the material properties. Biofilms were exposed to the chloride salts of several common mono-, di-, and tri- valent cations, and to urea, industrial biocides, and antibiotics. Many of these treatments resulted in statistically significant alterations in the material properties of the biofilm. Multivalent cations stiffened the P. aeruginosa biofilm, while ciprofloxacin and glutaraldehyde weakened it. Urea, rifampin, and a quaternary ammonium biocide weakened the S. epidermidis biofilm. In general, there was no correspondence between the responses of the two different types of biofilms to a particular treatment. These results underscore the distinction between the killing power of an antimicrobial agent and its ability to alter biofilm mechanical properties and thereby influence biofilm removal. Understanding biofilm rheology and how it is affected by chemical treatment could lead to improvements in biofilm control.
Chlorination of model drinking water biofilm: implications for growth and organic carbon removal
(2002-10) Butterfield, Phillip W.; Camper, Anne K.; Ellis, B. D.; Jones, Warren L.
The influence of chlorine on biofilm in low organic carbon environments typical of drinking water or industrial process water was examined by comparing biomass and kinetic parameters for biofilm growth in a chlorinated reactor to those in a non-chlorinated control. Mixed-population heterotrophic biofilms were developed in rotating annular reactors under low concentration, carbon-limited conditions (<2 mg/L as carbon) using three substrate groups (amino acids, carbohydrates and humic substances). Reactors were operated in parallel under identical conditions with the exception that chlorine was added to one reactor at a dose sufficient to maintain a free chlorine residual of 0.09¯0.15 mg/L in the effluent. The presence of free chlorine resulted in development of less biofilm biomass compared to the control for all substrates investigated. However, specific growth and organic carbon removal rates were on the average five times greater for chlorinated biofilm compared to the control. Observed yield values were less for chlorinated biofilm. Although chlorinated biofilm's specific organic carbon removal rate was high, the low observed yield indicated organic carbon was being utilized for purposes other than creating new cell biomass. The impacts of free chlorine on mixed-population biofilms in low-nutrient environments were different depending upon the available substrate. Biofilms grown using amino acids exhibited the least difference between control and chlorinated kinetic parameters; biofilm grown using carbohydrates had the greatest differences. These findings are particularly relevant to the fundamental kinetic parameters used in models of biofilm growth in piping systems that distribute chlorinated, low-carbon-concentration water.
Colonization and disinfection of biofilms hosting coliform-colonized carbon fines
(1996-12) Morin, P.; Camper, Anne K.; Jones, Warren L.; Gatel, D.; Goldman, J. C.
Colonization and disinfection of biofilms hosting coliform-colonized carbon fines
(1996-12) Morin, P.; Camper, Anne K.; Jones, Warren L.; Gatel, D.; Goldman, J. C.
Determination of a method for optimization of in situ biodegradability of subsurface soil contaminants
(1989-05) Jones, Warren L.; Bucklin, Karen Elizabeth; Camper, Anne K.
Diffusion and reaction within porous packing media: A phenomenological model
(1993-04) Jones, Warren L.; Dockery, Jack D.; Vogel, C. R.; Sturman, Paul J.
A phenomenological model has been developed to describe biomass distribution and substrate depletion in porous diatomaceous earth (DE) pellets colonized by Pseudomonas aeruginosa. The essential features of the model are diffusion, attachment and detachment to/from pore walls of the biomass, diffusion of substrate within the pellet, and external mass transfer of both substrate and biomass in the bulk fluid of a packed bed containing the pellets. A bench-scale reactor filled with DE pellets was inoculated with P. aeruginosa and operated in plug flow without recycle using a feed containing glucose as the limiting nutrient. Steady-state effluent glucose concentrations were measured at various residence times, and biomass distribution within the pellet was measured at the lowest residence time. In the model, microorganism/substrate kinetics and mass transfer characteristics were predicted from the literature. Only the attachment and detachment parameters were treated as unknowns, and were determined by fitting biomass distribution data within the pellets to the mathematical model. The rate-limiting step in substrate conversion was determined to be internal mass transfer resistance; external mass transfer resistance and microbial kinetic limitations were found to be nearly negligible. Only the outer 5% of the pellets contributed to substrate conversion. .
The effect of bacterial injury on toluene degradation and respiration rates in vapor phase bioreactors
(1997) Jones, Warren L.; Mirpuri, Rajesh G.; Lewandowski, Zbigniew; Cunningham, Alfred B.
The effects of prolonged toluene exposure and degradation on bacterial cultures of Pseudomonas putida 54G were investigated in three reactor systems: a batch suspended culture system, a bench-scale flat plate biofilm reactor, and a bench-scale packed column reactor. Humidified air containing 150 ppmv (toluene limiting) to 750 ppmv (oxygen limiting) toluene vapor was the sole source of carbon and energy supplied to these systems. Results from the suspended batch culture experiments were used to develop rate expressions and kinetic parameters for loss of culturability and of toluene degradative capacity. Experiments in the flat plate reactor were carried out to examine the effects of injury on biofilm structure and function. The packed column studies were performed under conditions relevant to field application, and confirmed results from the other two studies - that decreased culturability on toluene media correlated with decreased specific toluene degradation rate, particularly at higher toluene concentration.
Effect of growth conditions and substratum composition on the persistence of colifrms in mixed-population biofilms
(1996-11) Camper, Anne K.; Jones, Warren L.; Hayes, J. T.
Effects of carbon source, carbon concentration, and chlorination on growth related parameters of heterotrophic biofilm bacteria
(1999-11) Ellis, B. D.; Butterfield, Phillip W.; Jones, Warren L.; McFeters, Gordon A.; Camper, Anne K.
To investigate the growth of heterotrophic biofilm bacteria, a model biofilm reactor was developed to simulate a drinking water distribution system. Controlled addition of three different carbon sources (amino acids, carbohydrates, and humics) at three different concentrations (500, 1,000, and 2,000 ppb carbon), in the presence and absence of chlorine, was used in separate experiments. An additional experiment was run with a 1:1:2 mixture of the above carbon sources. Biofilm and effluent total and culturable cells, in addition to total and dissolved organic carbon, were measured in order to estimate specific growth rates (SGRs), observed yields, population densities, and bacterial carbon production rates. Bacterial carbon production rates (mg C/L day) were extremely high in the control biofilm communities (range = 295-1,738). Both growth rate and yield decreased with increasing carbon concentrations. Therefore, biofilm growth rates were zero-order with respect to carbon concentrations used in these experiments. There was no correlation between growth rate and carbon concentration, but there was a significant negative correlation between growth rate and biofilm cell density (r = -0.637, p = 0.001 control and r = -0.57, p = 0.021 chlorinated biofilms). Growth efficiency was highest at the lowest carbon concentration (range = 12 - 4.5%, amino acids and humics respectively). Doubling times ranged from 2.3 - 15.4 days in the control biofilms and 1 - 12.3 days in the chlorinated biofilms. Growth rates were significantly higher in the presence of chlorine for the carbohydrates, humics, and mixed carbon sources (p = 0.004, <0.0005, 0.013, respectively). The concept of r/K selection theory was used to explain the results with respect to specific growth rates and yields. Humic removal by the biofilm bacteria (78% and 56% for the control and chlorinated biofilms, respectively) was higher than previously reported literature values for planktonic bacteria. A number of control experiments indicated that filtration of drinking water was as effective as chlorination in controlling bacterial biofilm growth.
Estimation of cellular and extracellular carbon contents in sulfate-reducing bacteria biofilms by lipopolysaccharide assay and epifluorescence microscopic techni
(1994-11) Okabe, Satoshi; Nielsen, P. H.; Jones, Warren L.
Measurement of cellular and extracellular carbon contents of sulfate-reducing bacteria (SRB) is essential and important in studies of the role of SRB in corrosion and biofouling. An epifluorescence (EPI) microscopic technique and a lipopolysaccharide (LPS) assay were used to quantify cellular and extracellular carbon contents in Desulfovibrio desulfuricans biofilms. The average contents of lipopolysaccharide (LPS) and cellular carbon were 7.3 ± 2.8 (fg LPS) cell−1 and 39.9 ± 9.9 (fg cellular-C) cell−1, respectively, in a D. desulfuricans chemostat culture. A ratio of cellular carbon content to LPS content was 6.5 ± 2.8, and was used to estimate cellular carbon contents in a D. desulfuricans biofilm. The LPS and EPI methods gave comparable results for suspended samples, but not for biofilm samples.
An Evaluation of Condenser Tube Fouling at an Estuarine Nuclear Power Plant
(1988) McCaughey, M. S.; Thau, A.; Characklis, William G.; Jones, Warren L.
Growth kinetics of coliform bacteria under conditions relevant to drinking water distribution systems
(1991-08) Camper, Anne K.; McFeters, Gordon A.; Characklis, William G.; Jones, Warren L.
The growth of environmental and clinical coliform bacteria under conditions typical of drinking water distribution systems was examined. Four coliforms (Klebsiella pneumoniae, Escherichia coli, Enterobacter aerogenes, and Enterobacter cloacae) were isolated from an operating drinking water system for study; an enterotoxigenic E. coli strain and clinical isolates of K. pneumoniae and E. coli were also used. All but one of the coliforms tested were capable of growth in unsupplemented mineral salts medium; the environmental isolates had greater specific growth rates than did the clinical isolates. This trend was maintained when the organisms were grown with low levels (<1 mg liter-') of yeast extract. The environmental K. pneumoniae isolate had a greater yield, higher specific growth rates, and a lower Ks value than the other organisms. The environmental E. coli and the enterotoxigenic E. coli strains had comparable yield, growth rate, and Ks values to those of the environmental K. pneumoniae strain, and all three showed significantly more successful growth than the clinical isolates. The environmental coliforms also grew well at low temperatures on low concentrations of yeast extract. Unsupplemented distribution water from the collaborating utility supported the growth of the environmental isolates. Growth of the K. pneumoniae water isolate was stimulated by the addition of autoclaved biofilm but not by tubercle material. These findings indicate that growth of environmental coliforms is possible under the conditions found in operating municipal drinking water systems and that these bacteria could be used in tests to determine assimilable organic carbon in potable water.
Interspecies competition in colonized porous pellets
(1994-04) Sturman, Paul J.; Jones, Warren L.; Characklis, William G.
Packed-bed bioreactors filled with diatomaceous earth (D.E.) pellets were used to evaluate the effects of competition between inoculated and invading microbial species on the spatial and temporal distribution of microorganisms within an individual pellet. The (D.E.) pellets were cylinders 6 mm in diameter and 5–10 mm long with a mean pore diameter of 20 μm. Bench-scale experiments evaluated competition between two distinct microbial species: Pseudomonas aeruginosa, a motile, obligate aerobe (μmax = 0.4 h−1) and Klebsiella pneumoniae, a non-motile, facultative organism (μmax = 2.0 h−1). Organism growth rate appeared to be more important than motility or order of introduction in determining organism spatial and temporal distribution within the pellets. Pilot-scale experiments used pellets colonized with a pseudomonad growing on chlorobenzene as the sole carbon and energy source. Organic-rich ground water containing benzene, chlorobenzene and a population of indigenous microorganisms was used as feed. Pellet concentrations of the inoculated pseudomonad dropped from 109 to 106 colony forming units (cfu) ml−1 pellet volume over 15 days. These experiments demonstrate that inoculated organisms within porous packing media may undergo significant loss in colonization numbers when faced with competition from faster growing organisms.
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.
Physiological and chemical gradients in a pseudomonas putida 54g biofilm degrading toluene in a flat plate vapor phase bioreactor
(1997-11) Villaverde, S.; Mirpuri, Rajesh G.; Lewandowski, Zbigniew; Jones, Warren L.
A Pseudomonas putida 54G biofilm was grown on toluene vapor supplied as the sole external carbon and energy source in a flat plate biofilm reactor. Enumerations of cells in the biofilm were made using culture techniques (selective and nonselective for toluene) and microscopic techniques (total and respiring cells), and an analysis of the progression of the state of the culture was made by examination of various fractions of the populations. Long-term exposure to higher levels of toluene produced the following trends: (i) lower fraction of total cells that respired; (ii) lower fraction of culturable cells that also grew on toluene; (iii) higher fraction of respiring cells that could not grow on toluene plates; and (iv) a relatively constant fraction of total cells that could not be cultured on toluene. Respiration rate was determined using oxygen microsensors, and the fraction of the total respiration that was not associated with toluene uptake increased with higher toluene exposure. A combination of cryosectioning and respiration rate data was used to demonstrate that more respiring cells and a higher respiration rate both occurred at the base of the film, suggesting a deterioration in physiological state with continued exposure to toluene. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng56: 361–371, 1997.
Physiological stress in batch cultures of pseudomonas putida 54g during toluene degradation
(1997-06) Mirpuri, Rajesh G.; Jones, Warren L.; McFeters, Gordon A.; Ridgway, H. F.
Physiological stress associated with toluene exposure in batch cultures of Pseudomonas putida 54G was investigated. P. putida 54G cells were grown using a continuous vapor phase feed stream containing 150 ppmv or 750 ppmv toluene as the sole carbon and energy source. Cells were enumerated on non-selective (R2A agar plates) and a selective minimal medium incubated in the presence of vapor phase toluene (HCMM2). Differential recovery on the two media was used to evaluate bacterial stress, culturability and loss of toluene-degrading capability. A majority of the bacteria were reversibly stressed and could resume active colony formation on selective medium after passage on non-selective medium. A small fraction of the bacterial cells suffered an irreversible loss of toluene degradation capability and were designated as Tol− variants. Numbers of stressed organisms increased with duration of toluene exposure and toluene concentration and coincided with accumulation of metabolic intermediates from incomplete toluene degradation. Respiring cell numbers in the batch cultures decreased as injury increased, indicating a possible relationship between respiring and injured cells. Rate expressions for injury, for formation of Tol− variants and for growth of Tol− variants were determined by calibrating a theoretical model to the results obtained. These rate expressions can be used to calibrate bioreactor models, and provide a basis for better design and control of bioremediation systems.
Powdered activated carbon and biofiltration improve MF performance: Part I
(2007-05) Khan, Mohiuddin M. T.; Jones, Warren L.; Camper, Anne K.; Takizawa, S.; Katayama, H.; Kurisu, F.; Ohgaki, S.
This article shows how the use of high-dose powdered activated carbon and biofiltration are able to improve the performance of membrane-based microfiltration systems. The first part, which appears here, provides an overview of the study, materials and methods, and experimental design and operational conditions of the reactors.
Pretreatment for membrane water treatment systems: a laboratory study
(2003-08) Wend, Christopher Francis; Stewart, Philip S.; Jones, Warren L.; Camper, Anne K.
The goal of the work was to determine if biological treatment of water containing soil-derived humic substances has the potential for reducing the fouling of membranes used in water treatment. Laboratory scale biological filters containing biologically active carbon or iron oxide coated sand were fed humic-laden water with or without prechlorination. This stream was split, with half being further treated by microfiltration. Treated water was assessed for total organic carbon removal and biofouling potential using a glass bead assay and membrane assay for total cell counts, fouling layer thickness, and flux reduction. A combination of these assays provided more insight than any single measurement. Compared to untreated control water, biological treatment was capable of reducing downstream fouling of membrane systems. For example, fouling layer thickness was reduced by half after biological treatment, and cell counts were reduced four- to five-fold. Biological treatment coupled with microfiltration provided the best reduction of fouling, while prechlorination did not appear to impact the process. These results suggest that biological treatment may be valuable in reducing membrane fouling while reducing the amount of disinfectants used in pretreatment.