Closure with ecological engineering of a remote Cu/Zn concentrator: overview of 16 years R&D field program

Abstract

A 16 year field investigation to apply the principles of Ecological Engineering at a small, remote mining property, containing an estimated 0.75 million tones of acid-generating tailings, is described. The rehabilitation of the site relied heavily upon the performance of a biological polishing system established in a lake, acidified during mining operations. The effluents from the mill area, the underground workings and tailings seepages represent an estimated 15 t.y-1 of zinc and other metals in AMD, all directed into the 1 million m 3 lake. Ecological Engineering measures consisted of adding brush, phosphate, and calcium nitrate to the lake water and/or the sediments. And, since 1999, trials have been underway in the lake to determine the potential of using Mg to balance pH. The biological activity enhanced by these measures retains 80% of the zinc load within the polishing lake. The capital costs for a conventional high-density treatment plant have been estimated at $2.5 million (CDN) with annual operating costs of $0.35 million. To date, the cost of establishing a self-renewing, self-sustaining Ecolog