Ultraviolet disinfection system for constructed wetlands

Author

Jong Chan Ly

Graduation Date

2008

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, Environmental Systems: Environmental Resources Engineering, 2008

Committee Chair Name

Brad A. Finney

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Pacific Ocean--Humboldt Bay, Humboldt State University -- Theses -- Environmental Resources Engineering, Constructed wetlands, Disinfection, UV

Abstract

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 public health protection. However, ultraviolet (UV) disinfection systems have been recently adopted for wastewater treatment due to advantages over chlorination such as not creating Trihalomethanes (THMs), no odor, no danger of overdosing, not creating volatile organic 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, physical 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 suspended particles in the wastewater had diameters exceeding 50 m which UV can not penetrate, and over 90% of particles are smaller than 10m. 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.

https://scholarworks.calstate.edu/concern/theses/gf06g501x

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