REMEDIATION OF HIGH-STRENGTH MINE IMPACTED WATER WITH CRAB SHELL SUBSTRATE MIXTURES: LABORATORY COLUMN AND FIELD PILOT TESTS

Open Access
Author:
Grembi, Jessica Anne
Graduate Program:
Environmental Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 24, 2011
Committee Members:
  • Rachel Alice Brennan, Thesis Advisor
Keywords:
  • crab shell chitin
  • mine impacted water remediation
  • anaerobic passive treatment
  • alkalinity generation
  • metals removal
Abstract:
Anaerobic passive treatment systems remediating high-strength mine impacted water (MIW) have not displayed consistent success. For example, the high iron (140 mg/L) and acidity (380 mg/L as CaCO3) of the Klondike-1 discharge near Ashville, PA, caused premature clogging of a vertical flow pond which was filled with a traditional spent mushroom compost (SMC) and limestone substrate. In this study, continuous-flow columns and pilot-scale field reactors were used to evaluate if treatment of high-strength MIW can be improved using crab shell as a substrate amendment. For the lab study, continuous-flow columns containing 50– 100% crab shell (with the balance SMC) were compared to a sand control and a column containing the traditional 90% SMC and 10% limestone. MIW for the column study was obtained from the Klondike-1 site and pumped at a flow rate of 0.25 mL/min to maintain a 16 h hydraulic retention time within each column. After determining the best performing substrate mixture (70% crab shell + 30% SMC) in the column test, a pilot-scale field study was initiated, in which 1000-gallon tanks were filled with a limestone underdrain and an upper substrate layer of: 1) 100% crab shell; 2) 70% crab shell + 30% SMC; or 3) 90% SMC + 10% limestone. A fourth tank containing a sandstone underdrain with a 70% crab shell + 30% SMC substrate layer was installed to determine if similar performance could be achieved without the limestone underdrain. Aqueous samples were collected from the columns/reactors and analyzed for pH, ORP, ammonia, acidity, alkalinity, DOC, anions, and metals. Additional samples taken after passive aeration were also monitored. In the column study, the 70% crab shell + 30% SMC column treated double the volume of MIW, removed more than twice the mass of metals, and sustained pH above 5.0 for almost twice as long as the traditional SMC and limestone substrate. To date, the field study results mirror the laboratory findings.