Browsing by Author "Kessick, Michael A."
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Item Oxidation of aqueous sulfides in the presence of manganese dioxide(1974) Thomson, Bruce Merrill; Kessick, Michael A.A comparison of the oxidation potentials indicates that manganese dioxide is thermodynamically capable of oxidizing aqueous solutions cf hydrogen sulfide. A three part study was undertaken to: 1) determine the kinetics of the oxidation both in the presence and absence of oxygen, 2) measure the end products of the reaction, and 3), examine a possible treatment scheme using a fluidized bed of MnC2 particles. The oxichtion reaction was found to be first order with respect to the disappearance of sulfides under both aerobic and anaerobic conditions. The reactions are both pH dependent with the maximum rate occuring at pH 8.. By examining the products of the reaction, polysulfides, with x between 2 and 5) were found to be significant intermediates in both the aerobic and anaerobic situations and their presence is believed to explain the pH dependence. Under anaerobic conditions the quantity of manganous ions produced per sulfide ion oxidized is largely dependent on the end products of the reaction, which in turn depends on the pH. At pH 8 and below, sulfur is the primary end product and the ratio is equal to 1. Above pH 8 thiosulfate is farmed and the ratio is higher. When oxygen is present, the major product at the lower pH values is still elemental sulfur, and at pH 9, thiosulfate and sulfate anions are j jfound. In the presence of oxygen and high pH, the Mn ions are reoxidized, hence MnC2 acts as a catalyst in the reaction. In the fluidized bed experiments, good sulficfe removal was obtained at pH 7, 8, and 9 as long as the ratio was greater than 2. Mn++ ions were also reoxidized when the pH was greater than 8. Elemental sulfur was not formed, probably because the high degree of turbulence prevented nucleation. The principle products were sulfate at low pH and thiosulfate at higher values. Accordingly, a reaction scheme was proposed involving two competing reactions.Item Sad Sam in the cathedral of Atwater Kent(1976) Bay, Thomas Austin; Kessick, Michael A.Surface charge characteristics of filters capable of adsorbing viruses were studied. This was accomplished by microelectrophoresis of filter particle suspensions. The effect of pH on the surface charge properties of (1) cellulose nitrate, (2) cellulose acetate, and (3) fibreglass/epoxy filter materials was examined. It was discovered that these filter materials exhibited net negative charges over the pH range 2-7 when suspended in KC1/HC1 (or NaOH) solutions of ionic strength .2, with net negative charge approaching neutrality at the lower pH levels. The effects of various salts (KC1, MgC, CaC, AlCl) on the charge properties of cellulose nitrate were examined at pH 3.5 and pH 7.. It was observed that at both pH levels, increasing ionic strength caused the net negative charge of the filter material to approach neutrality. At a given ionic strength, the divalent and trivalent cations were more effective at decreasing the net negative charge of cellulose nitrate than the monovalent cations. The aluminum cations were actually capable of reversing the net charge of the filter material, from negative to positive. It was concluded that trivalent cations, and possibly divalent cations, are capable of complexing with specific groups on the filter surface. A mechanism for adsorption of viruses to filter surfaces was proposed. Complex formation between multivalent cations and specific groups on both viral and filter surfaces reduces the zeta potentials. This, coupled with a possible ionic strength effect on the configuration of the double layers, facilitates the approach of the two surfaces, allowing van der Waals attractive forces to exert a significant effect. With multivalent cations there is a further distinct possibility of cross-complexation between the two surfaces. It is proposed that cross-complexation by multivalent cations is more important than van der Waals forces in promoting attachment of the two surfaces, and that the action of the cations might be described in terms of a "cationic adhesive" effect. Electrostatic forces would be expected to oppose, but not prevent, cation promoted adhesion at neutral pH, when both virus and filter exhibit net negative charges. However, at pH 3.5, when the virus surface becomes net positively charged, electrostatic attractive forces would add to the "cationic adhesive" effect, resulting in highly efficient adsorption of viruses to filter surfaces.Item Surface change characteristics of virus adsorbing filters(1976) Wagner, Ray Arnold; Kessick, Michael A.Surface charge characteristics of filters capable of adsorbing viruses were studied. This was accomplished by microelectrophoresis of filter particle suspensions. The effect of pH on the surface charge properties of (1) cellulose nitrate, (2) cellulose acetate, and (3) fibreglass/epoxy filter materials was examined. It was discovered that these filter materials exhibited net negative charges over the pH range 2-7 when suspended in KC1/HC1 (or NaOH) solutions of ionic strength .2, with net negative charge approaching neutrality at the lower pH levels. The effects of various salts (KC1, MgC, CaC, AlCl) on the charge properties of cellulose nitrate were examined at pH 3.5 and pH 7.. It was observed that at both pH levels, increasing ionic strength caused the net negative charge of the filter material to approach neutrality. At a given ionic strength, the divalent and trivalent cations were more effective at decreasing the net negative charge of cellulose nitrate than the monovalent cations. The aluminum cations were actually capable of reversing the net charge of the filter material, from negative to positive. It was concluded that trivalent cations, and possibly divalent cations, are capable of complexing with specific groups on the filter surface. A mechanism for adsorption of viruses to filter surfaces was proposed. Complex formation between multivalent cations and specific groups on both viral and filter surfaces reduces the zeta potentials. This, coupled with a possible ionic strength effect on the configuration of the double layers, facilitates the approach of the two surfaces, allowing van der Waals attractive forces to exert a significant effect. With multivalent cations there is a further distinct possibility of cross-complexation between the two surfaces. It is proposed that cross-complexation by multivalent cations is more important than van der Waals forces in promoting attachment of the two surfaces, and that the action of the cations might be described in terms of a "cationic adhesive" effect. Electrostatic forces would be expected to oppose, but not prevent, cation promoted adhesion at neutral pH, when both virus and filter exhibit net negative charges. However, at pH 3.5, when the virus surface becomes net positively charged, electrostatic attractive forces would add to the "cationic adhesive" effect, resulting in highly efficient adsorption of viruses to filter surfaces.Item The biodegradation of particulate organic matter in saltwater media(1977) Seymour, Michael D.; Kessick, Michael A.The ocean environment is being used increasingly for the disposal of municipal sewage. Saltwater sewage systems are also in use in several locations. This research describes the microbially mediated degradation of the particulate fraction of sewage in saltwater media. Since the soluble fraction of sewage shows equal oxygen uptake, compounds thought to be representative of the particulate fraction of sewage were tested and found to be degradable in both freshwater and saltwater. Cellulose, however, did not seem to undergo reaction in saltwater within twenty days using organisms resident in domestic waste. Organisms from the marine environment were obtained and used to show that cellulose degradation was possible in saltwater media. Confirmatory data based on biomass and substrate depletion are accomplished using techniques developed for use in systems in which solid substrates are involved.Item Unit operations in salt water sewage treatment(1975) Manchen, Kenneth L.; Kessick, Michael A.A study was conducted to determine the effects of ocean salts on the nature and treatability of domestic sewage. The primary goal was to evaluate the effectiveness of physical chemical treatment, specifically chemical coagulation. One of the major analytical tests utilized in this work concerned the measurement of the chemical oxygen demand. The standard procedure was modified successfully for use in high salinity water. A minor modification was also employed in the determination of suspended solids. Formation of volatile suspended material was shown to occur upon introduction of sea salts to domestic sewage. The major compound precipitated was believed to be magnesium carbonate. Aluminum sulfate and lime were used in the coagulation studies. The results with aluminum sulfate demonstrated that coagulation with this chemical was more efficient when the ocean salts were present. Coagulation with lime was found to show the opposite effect. An additional and important result concerned the use of the biochemical oxygen demand test. Much lower oxygen demand values were found for unfiltered sewage after ocean salts had been added. Filtered sewage was found to exhibit the same oxygen demand whether or not the ocean salts were present. The lower values therefore appeared to be due to inhibition of breakdown of organic particulate matter.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.