Cleaning Up Little Laurel Run: Design and Performance of Different Crab shell Mixtures for Supporting Remediation of Acid Mine Drainage in Pilot-scale Reactors at the Klondike-1 Discharge
Open Access
Author:
Goots, Sara Sinclair
Area of Honors:
Environmental Systems Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Rachel Alice Brennan, Thesis Supervisor Mark Stephen Klima, Thesis Honors Advisor
Traditional means of remediating high-strength acid mine drainage (AMD) using vertical flow ponds (VFP) filled with spent mushroom compost (SMC) and limestone often display inconsistent success. The Klondike-1 treatment system on Little Laurel Run is one such example: the system was under-designed to handle the high iron (140 mg/L) and acidity (380 mg/L as CaCO3) of the discharge, and as a result, iron precipitates clogged the surface of the VFP in less than one year. Laboratory tests have shown that the addition of crab shell substrate can improve the efficiency of SMC, while still remaining cost effective. Therefore, a pilot-scale study was established at Klondike-1 to evaluate if the addition of crab shell to the existing VFP might improve treatment.
For the pilot study, four replicate 1,000-gallon reactors were installed at Klondike-1. Three reactors were filled with a limestone underdrain and an upper substrate layer of: 1) 100% crab shell; 2) 70% crab shell + 30% SMC; and 3) 90% SMC + 10% limestone. A fourth tank containing 70% crab shell + 30% SMC was installed with a sandstone underdrain to determine if similar performance could be achieved without the addition of limestone. In August, 2010, the pilot system went online and began receiving a continuous stream of AMD. After almost two years, the field study is nearing completion, with all tanks nearing exhaustion as designed. Net alkalinity remains highest in the 100% crab shell reactor (37 mg/L as CaCO3), and lowest in the reactor filled with the traditional SMC substrate (3.3 mg/L as CaCO3). The results of this study support the hypothesis that crab shell amended substrates increase the longevity and effectiveness of AMD treatment.
