Date of Award

5-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Hydrogeology

Committee Member

Dr. James W. Castle, Committee Chair

Committee Member

Dr. John H. Rodgers, Jr.

Committee Member

Dr. George M. Huddleston, III

Abstract

Constructed wetland treatment systems (CWTSs) have been used to renovate produced water (PW) from natural gas for reuse or discharge. The objectives of this study were to 1) characterize PW from coal bed methane (CBM), a type of unconventional gas, at a producing field in the Black Warrior Basin and identify constituents of concern (COCs); 2) design and construct an on-site demonstration CWTS to decrease COC concentrations; 3) assess treatment performance by measuring removal extents, efficiencies, and rates; and 4) compare treatment performance of wetlands with two organic carbon amendments (AquaSmartTM and shredded hardwood mulch). The demonstration CWTS design enabled treatment of COCs (ammonia, Ba, Cd, Fe, Mn) by targeting specific biogeochemical pathways, including nitrification and denitrification of ammonia to nitrogen gas, precipitation of Ba in the presence of sulfate, precipitation of Cd by sulfides produced through dissimilatory sulfate reduction, and oxidation and sorption of Fe and Mn. Concentrations of COCS in inflow and outflow of CWTS cells were measured bi-weekly for 6 months. Analyses of PW samples indicated inflow concentrations of 0.1-3.3 mg ammonia-N/L, 5.4-42 mg Ba/L, 0.11-0.28 μg Cd/L, 0.101-2.44 mg Fe/L, and 0.020-0.169 mg Mn/L. Constituent concentrations in CWTS outflow decreased consistently to less than water quality criteria (Clean Water Act guidelines; 1.4 mg ammonia-N/L, 1.0 mg Ba/L, 0.25 μg Cd/L, 1.0 mg Fe/L, and 0.05 mg Mn/L). Although inflow concentrations of COCs varied, achievement of water quality guidelines indicated a robust design for the demonstration CWTS. Because COCs encountered in this study occur in PWs associated with other types of unconventional gas, this treatment design should be applicable to many gas fields.

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