Date of Award

8-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Engineering and Earth Sciences

Committee Member

Dr. Ezra Cates, Committee Chair

Committee Member

Dr. David Ladner

Committee Member

Dr. David Freedman

Committee Member

Dr. Sudeep Popat

Abstract

Biofouling is considered to be one of the greatest operational challenges of reverse osmosis (RO) filtration for the production of potable water. Biofilms that form on the surface of a membrane filter quickly reduce the performance of the filter, and therefore these filters require constant treatment. Radioluminescence membrane biofouling control (RMBC) has been proposed as an alternative to the prevalence of chemical disinfection for the control of biofouling on RO units. Ultraviolet-C (200-280 nm) radioluminescence (UVC-RL) phosphors can convert a single beam of X-rays into large quantities of UVC. In RMBC, incorporating these phosphors into the feed spacers of an RO unit could allow for effective prevention of biofilm formation. In order to determine the dose of X-rays, and therefore the costs, of preventing biofouling with this technology, the critical UVC dose for biofouling prevention must first be experimentally derived. The objective of this study was to develop the procedures and methods for deriving the UVC dose-response required to prevent biofilm formation on membrane filters. This study required a lab-scale membrane cell that emulates an RO unit while also allowing the surface of the membrane filter to be continuously exposed to UVC radiation, but such an apparatus has not been developed. Therefore, a large portion of this research was designing and constructing this membrane cell. This membrane cell is a crossflow unit that has a built-in, high UV-transmitting, fused silica glass window. Once the membrane cell was constructed and proven to be capable of withstanding the flow of pressurized liquid, the continuous flow configuration for operating the membrane cell was established. Then, the experimental methods were developed for growing and quantifying biofilm grown by a model biofilm-forming organism (Escherichia coli ATCC 25922) on the membrane filter (polyvinylidene fluoride, 0.1 μm). Biofilm was shown to be quantifiable in terms of cell density (CFUs/cm2) and mass density (mg/cm2). Once these methods were established, the methods for deriving the UVC dose-response of biofilm prevention were also established. Though the UV dose-response itself was not determined in this study, UVC was able to reduced biofilm growth on the membrane surface in terms of 2-to-3 log removal. Using these methods, the research to find the UVC dose-response of biofouling prevention can start.

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