Semester

Fall

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

John Quaranta

Committee Member

Iuri Lira Santos

Committee Member

Nathan DePriest

Committee Member

Onur Avci

Abstract

A field scale mobile dewatering cell was constructed and demonstrated to investigate the filtration efficiency and dewatering characteristics of the cell. The cell was tested using hydraulic preconcentrate (HPC) from an active AMD treatment plant located in the Morgantown, WV area. HPC is a sludge-like material that comes from a two-stage treatment process of acid mine drainage, and it contains various rare earth elements. The cell was filled with HPC over time and the influent HPC and effluent water exiting the cell were tested each time the cell was filled. Taking these samples and other measurements, the filtration efficiency and discharge rate were measured. Once the cell was full of HPC, samples were taken on a weekly basis to measure the rate of dewatering which was measured in the percentage of total solids. A cost analysis of the mobile dewatering cell was conducted as well as triaxial testing of the HPC used to fill the cell. One consolidated-drained triaxial test was able to be conducted. The test showed an ultimate shear stress of 40 psi at 10.1 percent axial strain.

Throughout the filling process of the cell, the influent total solids percentage varied, ranging from 0.5 percent to 1.7 percent. The water exiting the cell consistently stayed at 0.2 percent total solids. Since 0.2 percent is the typical value for effluent from filtered HPC, the filtration efficiency was a function of the influent total solids percentage. The discharge rate from the cell ranged from 0.6 gpm to 7 gpm. As more solids were retained in the cell, the discharge rate was less, staying around 0.6 to 1.2 gpm for the last half of the fillings.

Once the cell was filled with solids, the total solids percentage of the HPC in the cell was investigated over time. First, a greenhouse cover was added to one half of the cell to investigate the differences in dewatering for a covered versus uncovered condition. The first samples taken average 4.7 percent total solids and reached an average of 21 percent total solids after a six-month period. The cell utilized two different capillary channel fiber (CCF) geotextiles, uniaxial and biaxial, as baffles to help aide in dewatering. Samples were taken from each row of CCFs as well as the middle that was open to compare the dewatering rate for each of those locations. At the start of sampling, there were minimal differences observed for the covered and uncovered sections of the cell, but as ambient temperatures became lower during fall and winter, the covered section dewatered quicker and had a higher total solids percentage. The biaxial and uniaxial CCFs dewatered the HPC at a similar rate throughout the course of sampling, indicating that the biaxial CCFs did not provide a significant advantage over the uniaxial CCFs.

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