Donald W. Sundstrom

Conversion of cellobiose to glucose using immobilized β-glucosidase reactors

Cellobiose is an intermediate in the enzymatic hydrolysis of cellulose to glucose and acts as an inhibitor for the cellulase enzymes. The conversion of cellobiose to glucose was studied with β-glucosidase adsorbed on Amberlite DP-1, a cation-exchange resin. The best overall pH for adsorption and reactor operation was near 5.0. The Km values increased with increasing enzyme loading due to competitive inhibition. The maximum practical enzyme loading was about 28 units/g resin. The immobilized enzyme was operated continously in both packed bed and fluidized bed reactors, giving half-lives between 200 and 375 h.

Thermal Conductivity of Reinforced Plastics

Thermal conductivity measurements were made with a Colora Thermoconductometer, which is described in detail by Schrbder [10]. A cylindrical test sample is placed between two silver plates that are maintained at constant temperatures by liquids with different boiling points. Saturated vapor from the liquid with the higher boiling point condenses on the lower silver plate and transfers energy to the sample. The liquid with the lower boiling point evaporates from the upper silver plate, and the generated vapor is condensed and collected in a graduated container.

Response of biological reactors to the addition of powdered activated carbon

Abstract A biological reactor operating on a synthetic feed was subjected to impulse and step disturbances of glucose and phenol. Powdered activated carbon was applied either as an impulse or as a step change to control reactor conditions. With glucose as the substrate, the addition of powdered carbon reduced the steady state TOC concentrations significantly but only slightly moderated the concentration transients after an upset. For impulse inputs of phenol, the simultaneous addition of carbon greatly reduced the magnitude of the transient changes in concentration. With step inputs of phenol, carbon addition rapidly lowered the phenol concentration in the reactor and permitted continuous operation with inlet phenol concentrations above 1000 mg 1 −1 . Thus, powdered carbon can provide an effective control method for maintaining effluent quality in the presence of toxic upsets.

Destruction of trichloroethylene by UV light-catalyzed oxidation with hydrogen peroxide

Abstract Advanced oxidation processes provide a destructive, economical alternative to conventional treatment methods for the removal of hazardous organic pollutants from groundwaters and industrial wastewaters. This project investigated the kinetics of trichloroethylene oxidation by ultraviolet light and hydrogen peroxide. The reaction rate of trichloroethylene was first order in ultraviolet light intensity and pseudo first order in trichloroethylene concentration. The rate was first order in hydrogen peroxide concentration at low peroxide levels, but independent of peroxide concentration at high peroxide levels. The maximum rate attainable depended on the reactor depth, with the shallower reactor yielding the larger maximum rate. A mechanism for trichloroethylene oxidation was proposed which yielded a rate expression consistent with the experimental observations.

The stability of activated sludge reactors with substrate inhibition kinetics and solids recycle

The steady-state simulation of activated sludge reactors with settler and recycle of the concentrated biomass was considered for the case of substrate inhibition kinetics. Analytical relationships were developed for the continuous stirred tank reactor; numerical simulation was performed for other reactors. Occurrence of multiple solutions and hysteresis behavior are examined as a function of space time θ, recycle ratio R, recycle solids concentration XR and sludge age θc. The sensitivity of the outlet substrate conversion with respect to the degree of substrate inhibition and of hydraulic mixing is discussed; criteria are suggested in order to operate such bioreactors and to prevent washout occurrence. All results are presented in dimensionless form.

The use of dimensionless groups in the design of activated sludge reactors

Abstract Dimensional analysis techniques were applied to the differential equations for a well mixed activated sludge reactor to obtain generalized information on the effect of process variables on conversion of substrate. The Monod model was used to represent the reaction kinetics since it also contains first and second order kinetics as special cases. The performance of a steady state reactor could be described in terms of five dimensionless groups involving the important combinations of process variables. A simple criterion was developed to predict washout conditions for reactors without recycle of biological solids. Under certain operating conditions, activated sludge reactors were shown to possess an inherent degree of self control to compensate for changes in feed concentration.

Physical property improvements of a pellicular biocatalyst

The thermal stability of an immobilization technique using a pellicular latex matrix was examined in a packed-bed column reactor. The stability was found to vary with liquid flow rate, the type of latex, temperature of operation, and the amount of yeast cells. Adjusting these parameters and introducing particulate inorganic fillers strengthened the latex matrix and improved the thermal stability. Optimization of this immobilization technique resulted in a procedure that allowed latex polymers to be mechanically stable at temperatures up to 50°C. The biological viability of this improved immobilization scheme was demonstrated through the production of L-aspartic acid by immobilized cells of E. coli.