ULTRAVIOLET DISINFECTION SYSTEM FOR CONSTRUCTED WETLANDS HUMBOLDT STATE UNIVERSITY By Jong Chan Ly A Thesis Presented to The Faculty of Humboldt State University In Partial Fulfillment Of the Requirements for the Degree Master of Science In Environmental Systems: Environmental Resources Engineering December, 2008 ULTRAVIOLET DISINFECTION SYSTEM FOR CONSTRUCTED WETLANDS HUMBOLDT STATE UNIVERSITY By Jong Chan Ly Approved by the Master’s Thesis Committee: Dr. Brad A. Finney, Major Professor Date Dr. Robert A. Gearheart, Committee Member Date Dr. Margaret Lang, Committee Member Date Dr. Christopher Dugaw, Graduate Coordinator Date Chris A. Hopper, Interim Dean Date Research, Graduate Studies & International Programs ABSTRACT ULTRAVIOLET DISINFECTION SYSTEM FOR CONSTRUCTED WETLANDS Jong Chan Ly Disinfection processes in wastewater treatment systems have been playing a vital role in protecting water resources from pathogenic microorganisms for decades. Currently the leading disinfection process is chlorination, which has contributed significantly to pub- lic health protection. However, ultraviolet (UV) disinfection systems have been recently adopted for wastewater treatment due to advantages over chlorination such as not creat- ing Trihalomethanes (THMs), no odor, no danger of overdosing, not creating volatile or- ganic compounds (VOC), and very little contact time. Although UV disinfection has been widely applied to conventional wastewater treatment, it is not common for constructed wetland wastewater treatment due to concerns of high effluent turbidity. This research was conducted to estimate the potential for UV disinfection technology in constructed wetland wastewater treatment. The Arcata Wastewater Treatment Plant (AWTP) was selected for this study because it is a wetland treatment system widely recognized for stable conditions and high quality effluent. The majority of samples were collected from the Pilot Marsh and samples from other treatment marshes were utilized for additional tests. During the research period, no fecal coliform was found after UV disinfection. This study also investigated possible concerns associated with UV disinfection: the effect of high UV dosage on algae population, the interfering substances of UV transmittance, phys- ical characterization of particles in the effluent of the marshes, and the potential for fecal coliform re-growth. This research found that algae death by UV light does not significantly contribute to effluent BOD. Also, the UV interfering substances (lignite and silt) in the Pilot Marsh do not influence the effectiveness of UV disinfection. Less than 1% of the iii suspended particles in the wastewater had diameters exceeding 50µm which UV can not penetrate, and over 90% of particles are smaller than 10 µm. In addition, UV disinfected samples showed no re-growing fecal coliform bacteria by photoreactivation or dark repair. Results of this research demonstrate that UV disinfection would be a highly viable option for AWTP. Further research is needed to estimate the applicable range of UV disinfection in different locations and environments. iv ACKNOWLEDGEMENTS My sincere appreciation goes to the many people who offered tremendous support and invaluable advice throughout this study. I would like to express my gratitude to my com- mittee members: Dr. Brad A. Finney, Dr. Robert A. Gearheart, and Dr. Margaret Lang. My main advisor, Brad, has been greatly supportive and has provided the remarkable guid- ance. I also thank Bob for his encouragement and excellent advice. My thesis would not be complete without Margarets contributions. I also would like to thank all the ERE fac- ulty and staff, especially Collin Wingfield, Marty Reed and Mary Jo Sweeters. The Arcata Marsh Research Members deserve special thanks: Mary C. Burke, who has been greatly inspirational, as well as Lucas Siegfried, Timothy Welgand, Gabriel Rossi, Jeff Woodke and Karen Wetherow. I would like to express my deep appreciation to my beloved family, my parents and my sister, for their endless devotion, patience, and love. Finally, I thank and praise God for all His work and love in my life. To them I dedicate this thesis. v TABLE OF CONTENTS ABSTRACT . iii ACKNOWLEDGEMENTS . v TABLE OF CONTENTS . vi LIST OF FIGURES . viii LIST OF TABLES . x INTRODUCTION . 1 Wetlands and Disinfection . 1 Wastewater Treatment System in Arcata . 2 LITERATURE REVIEW . 4 Disinfection of wastewater . 4 Chlorination . 5 Ultraviolet disinfection . 6 Constructed Wetlands . 9 The Effect of Particulate Matter on UV disinfection . 10 Coliform Re-growth . 13 The Effect of UV disinfection on Algae . 13 Humic Acid and UV transmittance . 15 Dose and Response of UV disinfection . 15 Design Factors of UV disinfection System . 18 Hydraulic properties of the reactor . 18 Intensity of the UV radiation . 20 Wastewater characteristics . 20 Main Parameters and Regulations . 21 Fecal Coliform . 21 Total Suspended Solids . 22 pH....................................... 22 Biological Oxygen Demand . 22 Regulations . 23 METHODS . 24 Study Site Description . 24 UV Disinfection Unit . 25 Sampling . 26 vi Water Quality Analysis . 26 Biochemical Oxygen Demand (BOD) . 26 Algae Survival . 27 Total Suspended Solids . 27 Fecal Coliform MF Method . 28 Ultraviolet Absorption Method . 28 Fecal Coliform Re-growth Test . 29 RESULTS AND DISCUSSION . 30 The Effect of UV Disinfection on Algae . 32 Algae Survival . 32 5-Day BOD . 33 Ultimate BOD . 35 UV Transmittance . 35 Particle counting test . 37 Fecal Coliform Re-growth Test . 38 CONCLUSION . 39 BIBLIOGRAPHY . 40 APPENDIX I . 45 vii LIST OF FIGURES Figure Page 1 Location of Arcata wastewater treatment plant (Roberts et al., 2008). 2 2 Arcata wastewater treatment plant with Arcata Marsh and Wildlife Sanctuary. 3 3 UV light in the electromagnetic spectrum (Washington State Department of Ecology, 2006). 7 4 Illustration of the effect of UV ray on DNA (Herring, 2006). 8 5 Effects of particles on UV disinfection (Blume and Neis, 2001). 11 6 Blue green algae (Anabaena) (Mount Allison University, 2000). 14 7 Examples of UV reactors : (a) Closed-channel and (b) Open-channel (US EPA, 2006). 19 8 Escherichia coli bacteria (Erbe, 2006). 21 9 Sampling Sites at Arcata Wastewater Treatment Plant. 24 10 Pilot UV disinfection unit (Double Helix UV sterilizer). 25 11 Fecal coliform counts from the Pilot Marsh (August 22, 2007 - December 20, 2007). 30 12 Total suspended solids from the Pilot Marsh (August 22, 2007 - December 20, 2007). 31 13 Dissolved oxygen results of Test I with sample Group A (R1: non-disinfected, A: 94.4 mJ/cm2, B: 121.9 mJ/cm2, C: 196.0 mJ/cm2). 32 14 Dissolved oxygen results of Test I with sample Group B (R1: non-disinfected, A: 94.4 mJ/cm2, B: 121.9 mJ/cm2, C: 196.0 mJ/cm2). 33 15 5-Day BOD and 10-Day BOD after UV radiation of Test I (R1: sample before UV radiation without seed, R2: sample before UV radiation with seed). 34 viii 16 Ultimate BOD results of Test I (A: 106.5 mJ/cm2, B: 126.6 mJ/cm2, C: 216.3 mJ/cm2). 36 17 Particle size distribution in percentage (Treatment marsh 3). 37 18 5-Day BOD and 10-Day BOD after UV radiation. (R1: sample before UV radiation without seed, R2: sample before UV radiation with seed). 45 19 Ultimate BOD results of Test II (A: 96.9 mJ/cm2, B: 125 mJ/cm2, C: 171.7 mJ/cm2). 46 20 Dissolved oxygen results of Test II with sample Group A (R1: non-disinfected, A: 106.5 mJ/cm2, B: 126.6 mJ/cm2, C: 216.3 mJ/cm2). 46 21 Dissolved oxygen results of Test II with sample Group B (R1: non-disinfected, A: 106.5 mJ/cm2, B: 126.6 mJ/cm2, C: 216.3 mJ/cm2). 47 ix LIST OF TABLES Table Page 1 Health effects of some by-products of chlorine disinfection (Bull, 1982). 5 2 Typical Mercury Vapor Lamp Characteristics (US EPA, 2006) . 8 3 Mercury Vapor Lamp Operational Advantages (US EPA, 2006). 9 4 Energy Requirements for UV Treatment Systems on Selected Organisms (The Northeast Midwest Institute, 2001). 16 5 Effluent limits for discharge to Humboldt Bay, Arcata Marsh and Wildlife Santuary (Kuhlman, 2007). 23 6 UV disinfection test results from the Pilot Marsh (August 22, 2007 - De- cember 20, 2007). 31 7 Dosage summary for effect of UV radiation on 5-Day BOD and 10-Day BOD. 34 8 Summary of average ultimate BOD results with various doses. 35 9 Summary of UV transmittance test results. 36 10 Summary of particle counting test results for each samples sites (TM2 : Treatment marsh 2, TM3 : Treatment marsh 3, EM : Enhancement marsh). 37 11 Summary of UV 10 day fecal coliform re-growth test results. 38 x INTRODUCTION Wetlands and Disinfection For decades environmental engineers have been concerned with the impact of treated waste discharges to natural water bodies to protect wildlife and public health. In particular, the level of bacterial contamination from wastewater on beaches and other recreational wa- ters has become critical. Every year thousands of shellfish beds are closed due to excessive levels of fecal coliform bacteria (McDonald et al., 2006). These issues have brought more attention to the need for disinfection of pathogenic organisms in wastewater treatment. Dis- infection processes generally use physiochemical treatment or chemical reagents. Chlorine is currently the most common disinfection chemical because of its high effectiveness in destroying pathogenic organisms and its economic feasibility. Over the last decade, the use of ultraviolet (UV) disinfection in wastewater treatment systems has rapidly increased due to cost competitiveness and advantages over chlorination including no by-product, no odor, no dechlorination needed, and safe and easy operations. Although UV disinfection has been widely used as an alternative disinfection process over the last decade, it is still generally limited to conventional treatment systems. UV disinfection is still not common for ponds and constructed wetlands due to a major concern that the high turbidity and total suspended solids of the wetland effluent would result in inadequate disinfection. Because of the significant concerns related to chlorination by-products and the large number of con- structed wetland systems, it would be worthwhile to study a UV disinfection system in a well-established constructed wetland treatment system.