Date of Award

5-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Yang Deng

Committee Member

Ranzun Zhao

Committee Member

Huan Feng

Abstract

Discharge of landfill leachate to publicly owned treatment works (POTWs) is a common and preferred practice in the United States. Namely, the leachate is mixed with municipal wastewater prior to traditional secondary wastewater treatment, including physical screening, primary settling, aerobic biological degradation, secondary settling and disinfection. Recently, ultraviolet (UV) light has been increasingly applied as a disinfection method at POTWs as an alternative for traditional chlorination, because the latter can produce unwanted disinfection byproducts. However, high strength dissolved organic matter (DOM) in leachate significantly increase the UV absorbing properties of the mixed wastewater at POTWs and decrease the disinfection efficiency of UV irradiation. Unfortunately, the origin and nature of the unique leachate-induced compounds are poorly understood. The objective of this study was to investigate UVquenching characteristics of landfill leachate. Typical leachate samples were collected from two landfills in Pennsylvania (PA) and North Carolina (NC). Column isolation tests were first used to fractionate DOM into humic acids (HA), fulvic acids (FA) and hydrophilic fractions (Hpi) in terms of their polarity. Subsequently, these groups were further separated using ultrafiltration techniques into different molecular weight (MW) groups (i.e. >100 kDa, 10-100 kDa, 1-10 kDa, and <1 >kDa). In both of the samples, results showed that the HA, FA, and Hpi all significantly contributed to the UV254 absorbance with the following order in terms of their significance: FA > Hpi > HA. However, HA had the highest specific UV absorbance at 254 nm (SUVA, defined as UV254/DOC) and UV254/COD, followed by FA and Hpi. The UV absorbance properties are most likely associated with aromatic degrees in molecular structures. In both samples, low MW leachate DOM (<1 >kDa) contributed to the most UV254 absorbance in all the fractions (HA, FA and Hpi) but the UV254 absorbance due to FA was the highest. In both samples, FA/DOC was observed in the PA leachate, but not in the NC leachate. These findings provide a better understanding of UV-quenching DOM in landfill leachate.

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