Date of Award

Spring 1-1-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Civil, Environmental & Architectural Engineering

First Advisor

Karl G. Linden

Second Advisor

James Rosenblum

Third Advisor

R S. Summers

Abstract

Hydraulic fracturing (HF) for oil and gas extraction is helping to meet worldwide changes in energy demand, but uses up to 13 million gallons of water per well, and generates a significant amount of high strength wastewater (HFWW). Onsite reuse of the wastewater can reduce the water intensity of HF through a combination of treatment and dilution. This type of reuse typically requires a reduction of suspended and colloidal material (turbidity), which can be accomplished with chemical coagulation (CC) and electrocoagulation (EC). In this study, EC was evaluated as a pretreatment option for a treatment train that could be used for onsite reuse of HFWW with a treatment goal of 90% reduction in turbidity and optimized reductions of the chemical oxygen demand (COD) and dissolved organic carbon (DOC). Design of experiments was employed to execute 32 experiments on a produced water sample that varied EC process control factors. Additionally, a dose-response curve was generated for CC with doses from 5 – 1,500 mg/L FeCl3 and AlCl3 as coagulants. The study evaluated the EC treatment impact on turbidity, COD, and DOC reduction. In addition, the treated water from four experiments was fractionated with membranes (10 kD, 5 kD, 1 kD) to evaluate the size of OM removed during EC and to compare them to chemically coagulated samples of the same water. For EC, turbidity reductions ranged from 74.6 – 97.3%, COD reductions ranged from 7.1 – 37.4%, and DOC reductions ranged from 5.7 – 54.0%; EC samples generally outperformed chemically coagulated samples, however, the dose-response curve indicates a high level of turbidity reduction with doses as low as 5 mg/L. Analysis of Variance (ANOVA) on experiments with the same electrode material revealed that the number of electrodes and amperage impacted treatment with EC most. The middle fraction (5 – 10 kD) saw the highest reductions in organic material and the smallest fraction (<1 kD) contained the most organic material but saw the smallest reductions. Electrocoagulation proved to be a suitable technology for turbidity reduction in a potential reuse scenario while achieving modest reductions in organic concentration that could be enhanced with another treatment technology after EC.

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