Publication Date

Spring 2012

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biomedical, Chemical & Materials Engineering

Advisor

Michael Jennings

Keywords

forward osmosis, hydrophobic membrane, membrane distillation, microporous membranes, osmotic distillation, osmotic evaporation

Subject Areas

Chemical engineering; Alternative energy; Aerospace engineering

Abstract

The osmotic distillation (OD) system is a spacecraft wastewater recycling system designed to produce potable water from human urine and humidity condensate. The OD system uses vapor-liquid separation to purify the wastewater across an osmotic distillation membrane, which is microporous and hydrophobic. When treating a mixture of urine and humidity condensate, the OD can produce water with a non-purgeable total organic carbon (NPTOC) concentration of less than 7 ppm; however, it is unclear what mechanism allows the system to achieve such a high total organic carbon (TOC) rejection when compared to other conventional distillation-based water treatment systems.

The hypothesis for this study was that osmotic agent concentration and feed pH influence TOC rejection in osmotic distillation. The objective of this research was to determine the effect of the ionic strength of the osmotic agent and the pH of the feed solution on TOC rejection. The feed pH values studied included 3, 7, and 10, and the osmotic agent concentrations studied were 20, 30, and 40 g/L (NaCl in water). The results of this research clearly indicated that feed pH had an effect on NPTOC rejection in osmotic distillation. The pH 3 treatments resulted in significantly higher TOC concentrations in the osmotic agent when compared to the feed pH values of 7 and 10. Based on statistical analysis, the osmotic agent concentration did not have an effect on TOC rejection in osmotic distillation.

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