Semester of Graduation

Spring 2024


Master of Science in Civil Engineering (MSCE)


Civil and Environmental Engineering

Document Type



Two pilot-scale anaerobic bioreactor (ABR) treatment systems were assessed for removal of chlorinated ethenes and ethanes from contaminated groundwater at a Superfund site in Massachusetts using full-scale ABRs for treatment of chlorinated volatile organic compounds (cVOCs). The treatment zone within the ABRs is comprised of a peat:sand porous media where removal of cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC) proceeded through to ethene and ethane as non-toxic end products. Maximum removal of cDCE and VC were ~0.7 mg/ft3·day and 2.4 mg/ft3·day, respectively. 1,1,1-trichloroethane degraded to 1,1-dichloroethane (1,1-DCA) via reductive dechlorination to chloroethane (CA). Reduction of 1,1-DCA took place toward the bottom of the treatment zone near the effluent port. Formation of CA was shown with increasing depth in the treatment zone.

The dechlorinating microbial community at work within the treatment media of each pilot-scale ABR was analyzed through sampling of the media at varying depths, and via sampling of the process water influent and effluent midway through the treatment zones. DNA extractions were conducted prior to amplification and targeted sequencing of the 16S rRNA gene in the V1-V9 region utilizing accurate long-read sequencing using the Pacific Biosciences Sequel IIe system. Amplicon sequence variants (ASVs) detected at sampled depths in the ABRs indicated abundance of class Dehalococcoidia dehalorespiring microorganisms increasing with distance into the treatment zones. Richness (defined as unique number of class Dehalococcoidia ASVs per sample) was as high as 8 in sampled media with two ASVs making up to 4.29% (D1) and 1.87% (D2) of the 16S total filtered reads. This diverse population of dehalorespiring bacteria have consistently met EPA discharge limits set for the site with limited energy inputs when compared with the previous mechanical treatment system. In addition, dominant populations within the sequencing dataset were assessed to better understand the presence of hydrogen-producing bacteria, as well as other functioning microorganisms contributing to the efficient removal of cVOCs in the anaerobic treatment zones.



Committee Chair

Pardue, John H

Available for download on Monday, January 04, 2027