(Where Oh Where Has The Water Gone?)
By Les Sawatsky, Femi Ade and Mike Bender
Raw water import requirements for oils sands mines depends mainly on factors such as ore processing rate, ore material characteristics, tailings processing technology, tailings storage systems, process water storage operations, the phase of tailings production, and several minor non-recoverable losses. These factors can be readily quantified to calculate raw water import needs. Nevertheless, confusion over consumptive uses often leads to a focus on recycling, which is irrelevant in a closed circuit water management system. Water conservationists improperly focus attention on raw water intake rules instead of the technical decisions that control consumptive uses. This paper presents a typical oil sands mine water balance for MFT to CT tailings operations, to illustrate the effect of controllable and uncontrollable parameters as well as major options that need to be explored for reducing water demand. Uncontrollable parameters include tailings sand and fines content of the ore, connate water, mine depressurization water inflows, net precipitation to the tailings pond, and surface drainage. Controllable parameters include storage operations, advance water supply ahead of mining operations, start of CT operations, net tailings pond seepage losses, and tailings impoundment operations. Potential raw water supply reductions may be achieved by providing greater on-site storage to attenuate water demand fluctuations , advance water storage prior to mine start up, early commencement of CT operations, and paste technology. The focus of water conservation measures should concern reduced on-site process water storage and water content of tailings material.
