Effective and low-cost treatment of acid mine drainage using chitin as a fractional amendment to compost
Open Access
- Author:
- Newcombe, Caroline
- Graduate Program:
- Environmental Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- April 02, 2009
- Committee Members:
- Rachel Alice Brennan, Thesis Advisor/Co-Advisor
Rachel Alice Brennan, Thesis Advisor/Co-Advisor - Keywords:
- spent mushroom compost
chitin
acid mine drainage
remediation - Abstract:
- This work presents the suitability of a mixture of two abundant, sustainable waste products of industry to support the remediation of acid mine drainage (AMD), an environmental pollutant that plagues mining areas all over the world. Low-maintenance, passive treatment systems hold the most promise for remediating AMD at a low cost relative to other treatment options. The choice of substrate in these systems is very important for successful remediation. Recently, our laboratory has shown that crab-shell chitin, a waste product of the shellfish industry, is capable of neutralizing acidity, reducing sulfate, and thoroughly removing aluminum, iron, manganese, and zinc from AMD. Despite its remarkable effectiveness, the relatively high cost of crab-shell chitin ($0.60/lb) compared to the leading substrate, spent mushroom compost substrate (SMS; $0.025/lb), may preclude its use in many systems. To facilitate the development of an effective but cost-efficient approach for AMD remediation, crab-shell chitin was used as a fractional amendment to SMS in this study. Two batch tests and a continuous-flow column test were used to evaluate different chitin-SMS mixtures for their ability to support AMD treatment. Natural AMD containing aluminum, iron, manganese, and zinc was used in these experiments, and aqueous samples were collected regularly for water quality analysis. In the batch tests, substrates containing only 5% chitin successfully generated alkalinity and partially removed metals from AMD. In the column experiment, the treatment capacity (as L AMD treated per kg of substrate used) for four different substrate mixtures was determined. Treatment capacities were: 36.7 L/kg for 10% limestone + 90% SMS; 40.1 L/kg for 5% chitin + 95% SMS; 162 L/kg for 50% chitin + 50% SMS; and 428 L/kg for 100% chitin. The associated substrate costs per 1000 L of AMD treated are: $1.38/1000 L, $2.95/1000 L, $4.25/1000 L, and $3.09/1000 L, respectively. These results suggest that a small fraction of chitin (5%) does not provide a significant benefit over traditional limestone and compost substrates, but that larger fractions of chitin (50-100%) are significantly more efficient than traditional SMS substrates, especially for the removal of metals.