Patricia A. Terry

Biosorption of cadmium and copper contaminated water by Scenedesmus abundans.

Experiments were conducted comparing the individual removals of cadmium and copper from water via biosorption using Scenedesmus abundans, a common green algae, to removal in a multi-component system to determine competitive effects, if any, between the metals. The goal was to characterize the biological treatment of water contaminated with heavy metals using live aquatic species. In addition, experiments were performed to measure cell viability as a function of metal concentration and also to compare metal removal using living species to that using nonliving ones. It was shown that, while both living and nonliving S. abundans removed cadmium and copper from water, living algae significantly outperformed nonliving algae. Further, in characterizing biosorption by three concentrations of live S. abundans, capacity curves were created comparing the metal biosorbed per mass algae to the initial metal concentration in solution. The algae concentration was not a factor in the biosorption of either metal individually, such that the capacity of the algae for the metal increased with decreasing algae concentration. At the lowest algae concentration considered, competitive effects were observed at copper and cadmium concentrations above 4 mg/l each. At the highest algae concentration considered, no competitive effects were observed in the range of cadmium and copper concentrations studied (1-7 mg/l). It was concluded that biological treatment of heavy metal contaminated water is possible and that at adequately high algae concentrations, multi-component metal systems can be remediated to the same level as individual metals.

Application of Ozone and Oxygen to Reduce Chemical Oxygen Demand and Hydrogen Sulfide from a Recovered Paper Processing Plant

A pilot study was performed at the Fox River Fiber recovered paper processing company in DePere, Wisconsin, to determine the extent to which injection of oxygen and ozone could reduce the high chemical oxygen demand, COD, in the effluent and the effectiveness of the ozone/oxygen stream in suppressing production of hydrogen sulfide gas in downstream sewage lines. Adaptive Ozone Solutions, LLC, supplied the oxygen/ozone generation and injection system. Samples were analyzed both before and after oxygen/ozone injection. Hydrogen sulfide gas was continuously monitored at sewer stations downstream of Fox River Fiber. Results showed that with a very short contact time, effluent COD was reduced by over 15%. A simple kinetic model predicts that a contact time of fewer than 30 minutes could reduce COD by as much as 60%. In addition, downstream hydrogen sulfide gas production in the sewage mains was also better controlled, such that costly Bioxide applications could be reduced.

Effect of Temperature, Zinc, and Cadmium Ions on the Removal of Cr(VI) from Aqueous Solution via Ion Exchange with Hydrotalcite

Experiments were conducted to determine and model the effect of cadmium and zinc ions in solution on the removal of Cr(VI) via ion exchange with hydrotalcite, a clay mineral media. Because many locations that have contaminated groundwater are located in colder climates, the ion exchange process was first characterized as a function of temperature. Binary solutions of Cr(VI) with either cadmium or zinc were investigated followed by a factorial design of ternary systems. Isotherms were modeled and used to compare removal of Cr(VI) in a single ion solution to multi-ion systems. Fixed-effect analysis of variance, PROC GLM (SAS Version 9), was used to analyze main and interactive effects. Results indicated that, while temperature did not significantly affect removal of Cr(VI), both Zn and Cd did reduce Cr(VI) ion exchange, most likely due to the formation of ionic complexes. Also, interactions between all three metal species ion the ternary system negatively affected removal of Cr.