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Lignor process for acidic rock drainage treatment.
1NORAM Engineering and Constructors Ltd., 200 Granville Street, Vancouver, B.C., V6C 1S4, Canada.
Environmental Technology
|November 2, 2004
Summary
The Lignor process effectively treats acidic rock drainage using lignosulfonates, a waste product. This method enhances sludge settling and stability while reducing lime consumption and sludge volume compared to traditional methods.
Area of Science:
- Environmental Engineering
- Water Treatment Technologies
- Industrial Waste Management
Background:
- Acidic rock drainage (ARD) poses significant environmental challenges due to metal contamination.
- Lignosulfonates, by-products of sulfite pulping, are explored as a treatment agent.
- Existing ARD treatment methods, like high-density sludge (HDS), have limitations in efficiency and sludge management.
Purpose of the Study:
- To evaluate the efficacy of the Lignor process for treating acidic rock drainage.
- To assess the role of lignosulfonates in improving lime performance and sludge characteristics.
- To compare the Lignor process with the high-density sludge process for ARD treatment.
Main Methods:
- Utilizing lignosulfonates to prevent lime coating and enhance dissociation.
- Incorporating lignosulfonates to improve sludge settling and dewatering rates.
- Implementing a multi-step Lignor process: metal sorption, lime neutralization, pH adjustment, air oxidation, and FeCl3 addition.
- Treating ARD from Britannia Mine, British Columbia, Canada.
Main Results:
- Lignosulfonates protect lime, promoting its dissociation and ARD neutralization.
- Addition of lignosulfonates significantly increases sludge settling and dewatering rates.
- The Lignor process effectively removes target metals (Al, Mn) below regulatory limits.
- Stable metal-lignin complexes are formed, enhancing long-term sludge stability against leaching.
Conclusions:
- The Lignor process offers a viable and advantageous alternative for ARD treatment.
- Lignosulfonates improve the efficiency and reduce the environmental footprint of ARD remediation.
- Key benefits include reduced lime consumption, smaller sludge volumes, and improved sludge stability compared to HDS.