We are committed to developing and utilizing leading-edge technologies, continually looking for ways to clean up impacted sites faster and at lower total cost than ever before. Our staff leads the industry in developing and publishing innovative technologies (see adjacent table) to treat many forms of environmental impacts. We hold more than 30 patents related to break-through treatment technologies, and are well known for our innovative, cost effective approaches to remediation.
This paper presents those technologies specifically applicable for remediating mining properties for both operating and closing sites. Case studies with results are included in the following sections.
Treatment of Pit Lakes and Flooded Underground Workings: Natural Pit Lakes
Many pit lakes resulting from cessation of mining activities contain elevated concentrations of dissolved metals. Traditional remedial options, such as backfilling, are extremely expensive and do little to mitigate groundwater impacted by flow through the pit. ARCADIS personnel have developed technologies that result in metals stabilization within the pit lake itself. The method involves adding organic carbon to stimulate in situ microbial activity, producing reducing conditions and the precipitation of metals as sulfides or in elemental form. This technique has been successful in removing mobile arsenic, cadmium,chromium, copper, iron, lead, manganese, mercury, nickel, selenium, silver, tin, uranium, and zinc to a solid, stable phase. Sulfate and nitrate concentrations are also significantly reduced.
ARCADIS technology goes further than other bioremediation treatment approaches that are being implemented by competitors. Our additional steps result in encapsulation of the precipitated metals, creating permanent immobilization and leaving a stable ecosystem that has been shown to maintain the stability of the immobile encapsulated metals. The technique involves encapsulating the precipitated metal compounds within an iron sulfide substrate, which can serve as a “sacrificial” redox buffer should redox conditions change with time within the pit lake or associated groundwater. Case studies are presented below.