Browsing by Author "Characklis, William G."

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Accumulation of a biofilm of k. pneumoniae and p. aeruginosa
(1989-12) Siebel, M. A.; Characklis, William G.
Activity of pseudomonas aeruginosa in biofilms: effect of calcium
(1989-01) Turakhia, Mukesh Harilal; Characklis, William G.
Aerobic glucose metabolism by Pseudomonas aeruginosa biofilms at various calcium loading rates was investigated. The influence of calcium on specific growth rate, extracellular polymeric substance (EPS) formation rate, biofilm detachment rate, and biofilm calcium concentrations was determined. Calcium accumulated in the biofilm in proportion to the liquid phase concentration. Increasing calcium concentration increased the cohesiveness of the biofilm as indicated by a lower relative detachment rate. Specific activity in the biofilm was the same as that measured in a chemostat and was not influenced by changing calcium concentration. EPS formation rate in the biofilm was unaffected by calcium concentration but was higher than that observed in a chemostat.
Activity of Pseudomonas aeruginosa in Biofilms: Steady State
(1984-12) Bakke, Rune; Trulear, Michael Gerald; Robinson, J. A.; Characklis, William G.
Aerobic glucose metabolism by Pseudomonas aeruginosa in steady-state biofilms at various substrate loading rates and reactor dilution rates was investigated. Variables monitored were substrate (glucose), biofilm cellular density, biofilm extracellular polymeric substance (EPS) density, and suspended cellular and EPS concentrations. A mathematical model developed to describe the system was compared to experimental data. Intrinsic yield and rate coefficients included in the model were obtained from suspended continuous culture studies of glucose metabolism by P. aeruginosa. Experimental data compared well with the mathematical model, suggesting that P. aeruginosa does not behave differently in steady-state biofilm cultures, where diffusional resistance is negligible, than in suspended cultures. This implies that kinetic and stoichiometric coefficients for P. aeruginosa derived in suspended continuous culture can be used to describe steady-state biofilm processes.
Algal Bioassay:Evaluation of Eutrophication Potential of Stormwater Runoff
(1976) Ward, C. H.; King, J. M.; Characklis, William G.; Roe, Frank L.
Algal-Bacterial Interactions Within Aggregates
(1982-10) Escher, Andreas Rainer; Characklis, William G.
Anaerobic srb biofilms in industrial water systems: a process analysis
(1993) Okabe, Satoshi; Jones, Warren L.; Lee, Whonchee; Characklis, William G.
Analysis and Monitoring of Heat Transfer Tube Fouling
(1982-10) Zelver, Nick; Flandreau, J. R.; Spataro, W. H.; Chapple, K. R.; Characklis, William G.; Roe, Frank L.
Attached microbial growths-I. Attachment and growth
(1973-08) Characklis, William G.
Water-soldi interfaces occur universally and are critically important in natural andindustrial processes. Microorganisms accumulate at these interfaces, frequently withbeneficial effects.A trickling filter can be described as a fixed bed reactor supplying a large amountof surface area used for the purification of organic waste of domestic or industrialorigin. Microorganisms attach to the packing material and form a reactive surface forthe adsorption and breakdown of the wastes. The benthos of natural streams carriesout an analogous process although this can be a significant drain on the oxygenresources of the stream.More often, however, microbial attachment is undesirable. Marine fouling isinitiated by the development of slimy films on submerged surfaces. The formation ofsuch primary films is believed to be a necessary precursor of heavy fouling (WOOD,1967) and is, at least in part, the result of microbial activity.
Attached microbial growths-II. Frictional resistance due to microbial slimes
(1973-09) Characklis, William G.
A number of cases have been reported in which water-carrying conduits have suffered from remarkable losses in delivery capacity within relatively short operation periods. In one instance (SEI~RT et al., 1950), the maximum capacity of a 24-in. (nominal diameter), 50 mile long water supply line was reduced to about 55 per cent of its original value within a few years. The loss was due to a thin, slimy layer that consisted largely of organic material imbedded with fine clay particles and was not caused by a substantial decrease in effective internal diameter. The layer was characterized by a "ripple-like" surface having an average height of 0.025 in. The results indicate that this type of roughness could not be explained in terms of equivalent sand roughness common to friction factor relationships.The rippled surface structure seems to be an essential, but not the only, factor involved in the unusual frictional behavior caused by microbial slimes. Experiments using solid surfaces of similar pattern have shown a high frictional resistance, but not nearly as high as those occurring in water mains.
Bacterial adsorption to smooth surfaces: Rate, extent, and spatial pattern
(1985-12) Nelson, Christopher H.; Robinson, J. A.; Characklis, William G.
The influence of bulk-water bacterial cell concentration and specific growth rate history on bacterial adsorption rates to surfaces was investigated using response surface analysis. A pure culture of Pseudomonas sp. 224s was grown in a chemostat and pumped into a continuous flow reactor where the bacteria were exposed to clean, glass surfaces under turbulent flow conditions for a periodof six hours. Adsorption rate decreased approximately linearly with increasing specific growth rate history. Glass surfaces became saturated with 2248 at ca. 0.1% coverage and the resulting spatial pattern of the adsorbed cells deviated from random in the direction of uniformity.
Bacterial Growth in Water Distribution Systems
(1988-11) van der Wende, E.; Characklis, William G.; Grochowski, J.
Bacterial Growth in Water Distribution Systems
(1988-02) van der Wende, E.; Characklis, William G.; Grochowski, J.
Biocide action of monochloramine on biofilm systems of pseudomonas aeruginosa
(1993-01) Chen, Ching-I; Griebe, Thomas; Characklis, William G.
Monochloramine was used to inactivate biofilm cells of Pseudomonas aeruginosa. Experimental results indicated that the clean RotoTorque system had no monochloramine demand. The dose of 4 mg·l−1 killed in situ biofilm cells more than 99·99% within 60 min, while the dose of 3 mg·l−1 killed 80% and the dose of 2 mg·l−1 showed no significant killing. Computations of pseudo steady state surface gradient of monochloramine and the observable modulus indicated that there was no marked mass transfer resistance in the biofilm for the 4 mg·l−1 treatment, moderate mass transfer resistance for the 3 mg·l−1 treatment, and high mass transfer resistance for the 2 mg·1−1 treatment. Mass transfer resistance within the biofilm impacts the biocide performance.
Bioengineering Report/Fouling Biofilm Development: A Process Analysis
(1981-09) Characklis, William G.
Biofilm development at a surface is the net result of several physical, chemical, and microbial processes including the following: (1)transport of dissolved and particulate matter from the bulk fluid to the surface; (2) firm microbial cell attachment to the surface; (3) microbial transformations (growth, reproduction, etc.) within the biofilm resulting in production of organic matter; (4) partial detachment of the biofilm due primarily to fluid shear stress. This report presents a framework for analyzing the interrelated processes contributing to biofilm development. Some of the available rate and composition data are presented so that the relative process rates can be compared.
Biofilm accumulation and activity: a process engineering analysis
(1992) Bryers, James D.; Characklis, William G.
Process Analysis refers to the application of systematic methods to recognize, define and clarify problems and to develop methodologies for their solution. Biofilm formation and persistence in both natural and engineered systems is governed by a collage of complex physical, chemical, and biological processes; each process dependent on a unique set of system parameters. Process analysis applied to biofilm formation provides an integrated approach which incorporates microbial physiology, reaction engineering, and transport phenomena to understand, control, and exploit biofilm processes. Application of process analysis allows one to (a) interpret the operation of an existing biofilm system, (b) design new biofilm reactor systems, and (c) understand the complexities of natural biofilm systems. It is increasingly apparent that research into biofilm processes which does not comprise microbial, chemical, and fundamental engineering aspects is incomplete.
Biofilm and Their Effects on Local Chemistry
(1988-10) Characklis, William G.; Little, Brenda J.; McCaughey, M. S.
Biofilm developement and destruction in turbulent flow
(1979-01) Characklis, William G.
Biofilm development and destruction in turbulent flow
(1979) Characklis, William G.
Methods for direct and indirect measurements of biofilm development (fouling) are presented. Laboratory systems were developed to determine rate and extent of fouling as a function of wall shear stress, water quality, and bulk temperature. Experimental systems were also developed to evaluate the effects of oxidizing biocides and to compare their relative efficiency.
Biofilm development: a process analysis
(1984) Characklis, William G.
Biofilm growth and hydraulic performance
(1980) Picologlou, B. F.; Zelver, Nick; Characklis, William G.
An experimental investigation of the deleterious effect of microbial slime layers on the hydraulic performance of water conduits is presented. The underlying mechanisms that lead to an increase of frictional losses in the conduit are explored and their relative importance is discussed. It is shown that although the slime layer is viscoelastic and filamentous, its effect on frictional resistance can be adequately represented through an increase in rigid equivalent sand roughness of the conduit wall.