September 1, 2010

Mine Drainage: An Alternative Source of Water

Robert L. Zick

First-Rate Pilot Study Results

A pilot unit that was run to demonstrate the AMDRO process system showed the technology significantly reduced the chemical demands in the process while achieving the product quality and reliability required. Though the technology was able to operate at 60% to 65% water recovery, compared to 78% recovery achieved by the conventional approach, the operating costs were greatly reduced. The impact on the mine water of the added sodium in the softening process to the concentrate was also eliminated. The reject from the conventional treatment process contained approximately 7.4% sodium sulfate.

The calculated chemical cost for the AMDRO technology was significantly less (Table 1), although capital costs were very similar. Less equipment was required with the AMDRO process, but a higher-grade construction material was required for operation at a pH of 2.5.

Table 1. Comparison of conventional and AMDRO water treatment costs for treating acid mine drainage for power plant makeup water use. Source: Veolia Water Solutions & Technologies Inc.

The pilot study showed that iron and other metals could be maintained in solution and they were effectively rejected by the RO membranes, brought down to the low levels that would be required for the power plant feedwater by using a second-pass RO bank (Table 2).

Table 2. Pilot plant test results using AMDRO to treat acid mine drainage. Source: Veolia Water Solutions & Technologies Inc.

The pilot study demonstrated that AMDRO technology could be effectively used, in this case, to produce the quality of water required for the power plant—and at significantly lower chemical costs and lower sludge production than the conventional approach. It would also have less of a long-term impact on the quality of the mine water, due to the recycling of concentrates back into the mine pool.