Browsing by Author "Characklis, William G."
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Item Biofilm development and associated energy losses in water conduits(1979) Zelver, Nicholas; Characklis, William G.; Bedient, Philip B.; Picologlou, Basil F.Microbial film development in water conduits causes pronounced increases in fluid frictional resistance and heat transfer resistance which is of major concern to the water supply and power industries. The objective of this study was to better understand the microbial film development process and its effect on fluid frictional resistance. A Tubular Fouling Reactor system was constructed to investigate microbial film development in the laboratory. Glucose was used as the energy source for microbial growth. Fluid frictional resistance in the fouled tube increased to as much as eight times the clean tube condition. Constriction of the tube due to the microbial film does not significantly affect fluid frictional resistance. However, viscoelastic properties and the filamentous nature of the microbial film contribute to the increase in fluid frictional resistance. Growth kinetics and substrate removal were investigated and a model for microbial film production was developed. Experimental data were used to test the validity of the model and good agreement was obtained. The results indicate that fluid frictional resistance and microbial film thickness can be predicted from influent glucose concentration for a given flow velocity.Item Control of microbial fouling in circular tubes with chlorine(1976) Norrman, Gunilla; Characklis, William G.Microbial attachment to liquid-solid interfaces has detrimental effects in flow systems. Frictional resistance shows a pronounced increase due to microbial films and thus causes higher energy requirements for fluid transport. The objective for this study was to obtain basic information about attachment and growth of bacteria and destruction of existent slime layers on the walls of a tubular reactor. Results indicate that high pressure drops caused by film formation cannot be explained by the resultant decrease in tribe diameter. The microbial film is assumed to have a rippled surface and viscoelastic properties which explain large increases in frictional resistance. Friction factors are as much as three times as high as in the clean tube. Chlorine was used as a slimicide to prevent fouling and remove formed slime layers. Results indicate that chlorine effectively removes microbial films if added at relatively high concentration for a short period of time at least once a day or at low concentrations with continuous addition. Shock chlorination every other day was not sufficient to prevent extensive fouling between chlorinations. Chlorine utilization by the film was shown to be dependent on concentration of chlorine feed and flow rate suggesting that slime control efficiency could be improved by increasing flow rate during chlorination. Chlorine utilization rate was not dependent on film thickness. A computer model for microbial fouling was developed. Experimental data were used to test the validity of the model and good agreement was obtained.Item Dissimilatory sulfate reduction in anaerobic aqueous systems(1973) D'Alessandro, Peter Louis; Characklis, William G.This research presents stoichiometric and kinetic data describing the consumption of substrate and sulfate in pure and mixed microbial cultures. Data were obtained for pure cultures of Desulfovibrio vulgaris and Escherichia coli in the presence of glucose and lactate. Lactate and sulfate were consumed in a stoichiometric ratio of 2:1 by D. vulgaris in both pure and mixed culture. The mixed culture experiment simulates the microbial interactions that lead to crown corrosion in sewers and to "sour" conditions in anaerobic digesters. A novel approach for sulfide control by oxidation with granular manganese dioxide was studied. In a cell free system, the reaction proceeded on a first order basis over the course of one half-life. Heterogeneous cultures of sulfate-reducers were grown in the presence and absence of granular manganese dioxide. Examination of the differential sulfide yield suggests that neither the rate nor the order of the reaction is altered.Item Fate of cyanide in aerated microbial systems(1975) Raef, Stuart Finley; Characklis, William G.The relative importance of four interrelated possibilities for cyanide removal in aerated microbial systems was investigated. In an aerated system at neutral pH with both cyanide and glucose present, the relative importance for cyanide acclimated heterogeneous cultures appears to be? 1) stripping; 2) biological metabolism? 3) adsorption onto biological floe, and? 4) chemical reaction in solution with substrate. At higher pH, chemical reactions in solution become significant. The chemical reaction of cyanide with substrate was investigated in sealed glass ampoules using glucose as substrate and inorganic buffers. The reaction was found to be pseudo-first order and pH dependent, with an optimum pH near 11.. The cyanide-glucose reaction products were found to be biodegradable by both acclimated and unacclimated heterogeneous cultures in shake flask and BOD bottle systems. Adsorption properties were investigated using sealed, stirred glass reactors containing bacteria and potassium cyanide in water buffered at pH 7. with inorganic buffers. Very little adsorption was evidenced after one hour in reactors containing a starved nonflocculating pure culture of Bacillus megaterium.ATCC Strain 23. However, up to 15 percent adsorption occurred in systems containing a stirred flocculent heterogeneous culture. Thus, biological adsorption effects are relatively unimportant as a cyanide removal mechanism. Stripping effects were investigated using starved heterogeneous bacteria in an aerated microfermenter at neutral pH. Cyanide and carbon dioxide in the off-gas were trapped in sodium hydroxide solution, separated, and analyzed. Stripping removed up to 8 percent of original cyanide, and tests using K14CN revealed that a small amount of cyanide was metabolized. Cyanide metabolism was studied using starved, acclimated heterogeneous cultures in an aerated microfermenter containing glucose as substrate. Tests using K14CN showed that up to 5 percent of the cyanide was metabolized as evidenced by 14CO2 production. Bacillus pumilus and Bacillus mecraterium did not aero bically metabolize significant quantities of glucose, but both species metabolized tryptic soy broth in the presence of up to 1 mg/1 cyanide (as CN).Item Hydrologic simulation of storm water detention storage in an urbanizing flood-plan(1980) Smith, David Paxton; Bedient, Philip B.; Characklis, William G.; Rowe, Peter G.Emerging concepts of urban flood control consider the use of storage detention, especially where channel capacities are being overtaxed by urban runoff. Particular problems exist where high rainfall intensities and low topographic relief combine with rapid urban development to produce potential flooding. Traditional approaches to flood control emphasize channelization of main streams and laterals to speed urban runoff out of developed areas. However, in low relief areas where the effect of urban drainage may be to greatly increase the peak flow rate and decrease the time to peak, flood control solutions of the 195's cannot handle the increasing development of the 197's. This has been experienced in rapidly growing coastal cities such as Houston, Texas. The purpose of the present study is to analyze the effect of detention storage placement and design on downstream flood flows in an urbanizing watershed. Effects of rainfall frequency, land use condition, and storage policy are directly considered in the methodology. The approach can be applied to any urban watershed in which historical rainfall data and streamflow data as well as land use information is available. The U.S. Army Corps of Engineers HEC-1 Model forms the basic tool for analysis of flood flows. A storage detention model is used in conjunction with empirical unit hydrographs which are derived as functions of land use. Storage detention is tested in both existing urban areas as well as projected future developments to discover effects on flood frequency flows. It is concluded that the ability to reduce the flooding potential of a rapidly urbanizing watershed with detention storage is limited by topography, remaining open space, and the presence of downstream development.Item Influence of temperature on biofilm processes(1981) Stathopoulos, Nikos A.; Characklis, William G.; Tomson, Mason B.; Papoutsakis, T.Biofilm development on surfaces exposed to aqueous environments usually causes an increase in fluid frictional resistance, heat transfer resistance, and corrosion which are of major concern to the water supply and power industries. The objective of this study was to investigate the effect of temperature, an important environmental factor, on the biofilm processes. A tubular fouling reactor system was used for this experimental study. Trypticase Soy Broth was added to the reactors providing the necessary growth requirements for a mixed culture of four bacterial species. A model with the appropriate material balances was developed for the experimental system. Six different temperatures (15-5°C) were tested and their effects on the rate coefficients are reported. An optimum temperature range for biomass growth and for the microbial process occurring within the biofilm was found.Item Ozonation of tannic acid(1976) LeBlanc, Janice Marthe; Characklis, William G.The oxidation of tannic acid by ozone was studied in a continuous flow, stirred tank reactor at steady state. Reaction products were characterized by the following analyses: chemical oxygen demand (COD), total organic carbon (TOC), and biochemical oxygen demand (BOD). Results indicate that ozonation of tannic acid reduces COD, TOC, and BOD.Item Studies on a dual-organism dual-substrate biological reactor(1974) Batchelor, Bill; Characklis, William G.A dual-organism, dual-substrate microbiological reactor was studied using organisms which metabolize either phenol or methanol. The growth characteristics of yield, ratio of oxygen to substrate uptake rates (RO2/Rs), unit rate of oxygen uptake (RO2/Cb), and substrate concentration were evaluated as functions of growth rate in cultures with a single species predominating (SSP) and with a mixture of the two organisms. In both SSP cultures yield and RO2/RS were decreasing functions of growth rate, indicating an increased tendency of the organisms to excrete metabolic by-products at increased growth rates. Ro2/Cg in both cultures was a linear increasing function of growth rate as expected. Both yield and Ro2/R in the mixed culture were lower than in the SSP, indicating an increased tendency toward by-product excretion. The methanol organism indicated the existence of a positive interaction with the phenol organism in mixed culture. The dehydrogenase activity test was unable to predict the relative amounts of phenol and methanol organism in the mixed culture due to excessive variability in SSP cultures and inability to measure phenol organisms activity in mixed culture. The stoichiometry of microbial oxidation of methanol and phenol was found to vary with growth rate but was complicated by possible by-product formation.Item The effect of dissolved oxygen tension on the stoichiometry of a microbial reaction(1976) Curtis, Marc Andrew; Characklis, William G.The effect of dissolved oxygen tension (DOT) on microbial cultures in wastewater treatment processes has been a controversial subject for the last two decades. Expanded application of the pure oxygen activated sludge process has developed data that centered the controversy around two issues: the effect of DOT on culture stoichiometry and the effect of DOT on settling rates of biological floes. This work investigates the stoichiometric effect of DOT. A carbon balance method was developed to monitor the stoichiometry of a continuous culture by analyzing influent and effluent, gas, liquid, and solid streams for carbon. Over the DOT range studied (3-4 mg/l) there was no direct effect of DOT on the stoichiometry. High DOTS did affect the balance of predators and prey in the culture by inhibiting the ciliates. In this way DOT indirectly affected the stoichiometry. Carbon dioxide concentrations varied unavoidably in the aeration gas providing the opportunity to analyze its effect. From limited data it appears to have a direct effect on stoichiometry with increased carbon dioxide inhibiting respiration.Item Variations in glucose diffusion coefficients in biological flocs(1974) Pipes, David Meggs; Characklis, William G.; Hellums, Jesse D.; Kessick, Michael A.The diffusion coefficient of glucose was measured in biological flocs under various growth conditions. Significant differences were observed with different carbon sources and carbon to nitrogen ratios. The diffusion coefficients were calculated from direct measurements of mass flux through a series of membrane filters separated by a metal template which contained the floe. The template assembly was prepared by packing the floe material into the template and placing a .45|j, membrane filter on either side of the template. The assembly was then placed in a modified plastic Millipore filter apparatus having the lower portion filled with a glucose solution (1 mg/1) and the top section containing deionized water. Increasing glucose concentration in the top was related to mass flux through the floe by measuring the flux through the membrane filters separately. Measurements were replicable within 8%. A 2^3 factorial analysis, using carbon source (glucose or methanol), carbon to nitrogen ratio (5:1 or 5:1), and temperature (2°C or 3°C) as independent variables, indicated significant effects at the 99% level for all three variables.