Microorganisms that cause plant disease have been isolated in recirculated irrigation water and increase the risks of disease incidence in horticultural operations. Ozone is an effective oxidizer used to disinfect drinking water supplies and treat industrial wastewater. The objective of this research was to investigate using ozone gas as part of a strategy to reduce the incidence of Phytophthora deBary in recirculated irrigation water. An isolate of Phytophthora capsici Leonian was cultured to induce sporulation. Spore dilutions were placed in aliquots of reverse osmosis water and bubbled with ozone gas (O3) to concentrations of 0 to 1.5 mg·L-1. Ozonated samples were plated and observed for colony forming units. Increasing ozone concentrations reduced the number of colony forming units to 0 at 1.5 mg· L-1 03. Turbidity effects on efficacy on Phytophthora capsici were tested using bentonite clay at 0 to 2.0 nephelometric turbidity units and ozone concentrations of 0 to 1.5 mg· L-1. Increasing bentonite did not affect the efficacy of increasing ozone concentrations on reducing colony formation to 0 at 1.5 mg·L-1 O3. Bioassays using Phytophthora capsici on Capsicum annuum L. seedlings confirmed apparent pathogenicity. Reverse osmosis water, containing a soluble fertilizer at 0 to 300 mg· L-1 N, was ozonated to concentrations of 0 to 1.5 mg·L-1 O3 and used to irrigate Chrysanthemum x morifolium T. de Romatuelle. Increasing ozone concentrations did not interact with increasing fertilizer levels to affect the final growth parameters. Chrysanthemum exposed to ozone gas concentrations of 0.5 to 1.5 mg·L-1 showed symptomatic ozone damage. Complete soluble fertilizer solutions with micronutrients were ozonated from 0 to 1.5 mg·L-1 O3 and analysed for nutrient content. Increasing ozone levels did not interact with fertilizers to affect macronutrients. Increasing ozone interacted with iron at a high fertilizer level. Ozone did not affect the efficacy of paclobutralzol in controlling growth in Viola x wittrockiana. Ozone was effective in controlling Phytophthora capsici in recirculated irrigation water with minimum impact on plant growth. Adjustments in fertility regiemes may be needed to counteract the oxidizing affect of ozone on micronutrients.

Constructed wetland system is a natural purifying procedure of management and disposal of water and wastewater by means of Ecological Engineering Technology. Neither additional chemical agent nor mechanical equipments and electrical power are needed in the procedure of water quality purifying. It is also a potential Ecological Engineering Technology with advantages of low-cost, easy operation and management, and easy construction. However, the limitation of this technology is the requirement of larger land space for wetland construction. Taiwan features in a subtropical climate, moderate water temperature, abundant sunlight, so its environmental condition is a good fit for constructed wetland technology, which has been verified by numerous pilot and field scales studies in recent years. Due to the necessity of large land space, it is impossible to apply it in the urban environment that is densely populated. In the rural area of Taiwan, however, with the industry development or industry moving outside, there appears a lot of fallow lands, idle lying factories. Moreover, the undeveloped construction of sewage work in Taiwan (especially in rural areas) results from inadequate construction expenditure supported by government, while discharge raw sewage in urban causes water pollution and water shortage. Hence, if we could establish constructed wetlands in the programmed proper places (such as presumptive address in parks or low-rent fallow lands), less construction expenditure could be used to construct sewage work and to protect water resource. After the proper programming and management, constructed wetland has multiple functions such as sightseeing, recreation, and ecology education. In order to explore the possibility of domestic wastewater disposal by constructed wetlands, the research adopted three ecological engineering treatment systems: Erhang constructed wetland system, Gangwei constructed wetland system, and Dajia soil filtration system. In this study, the treatment efficiencies and effectiveness of water quality improvement via these three systems were investigated. Results from the monitoring results of the influents and effluents of these systems were evaluated. In the Erhang constructed wetland, results were collected from July 2004 to October 2005. During this investigation period, the average flow rate was 52 CMD, and the observed biochemical oxygen demand (BOD) removal efficiency and removal rate were 72¡Ó22¢H and 1.68¡Ó1.12 kg/day, respectively. In the Gangwei constructed wetland, results were collected from July 2004 to May 2006. During this investigation period, the average flow rate was 61.6 CMD, and the observed BOD removal efficiency and removal rate were 33¡Ó40¢H and 0.14¡Ó0.19 kg/day, respectively. In the Dajia constructed wetland, results were collected from July 2004 to May 2006. During this investigation period, the average flow rate was 21.92 CMD, and the observed BOD removal efficiency and removal rate were 79¡Ó16¢H and 0.9¡Ó0.5 kg/day, respectively. Results from this study indicate that the three systems could effectively remove the main pollutants in inflow water and the treated water is able to meet the discharged standards. Thus, the constructed wetland scheme has the potential to be developed into an environmentally and economically acceptable domestic wastewater treatment technology. Results from this study will be useful to assist environmental professionals in designing a scale-up system for future application.

Thesis (Ph. D)--Ohio State University, 2002. / Title from first page of PDF file. Document formatted into pages; contains xxii, 119 p.: ill. Includes abstract and vita. Advisor: Harold W. Walker, Civil Engineering Program. Includes bibliographical references (p. 115-119).

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Gerontology / Master / Master of Social Sciences

published_or_final_version / Community Medicine / Master / Master of Public Health

published_or_final_version / Public Health / Master / Master of Public Health

published_or_final_version / Public Health / Master / Master of Public Health

published_or_final_version / Surgery / Master / Master of Medical Sciences

published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy