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Recycling Water with Zero Liquid Discharge at Mackay River

Suncor’s MacKay River in situ facility is demonstrating the only fully-functional Zero Liquid Discharge (ZLD) system in the oil sands industry. ZLD has a number of benefits, such as recycling more than 90 per cent of the facility’s water.

Like most in situ operators, Suncor uses steam assisted gravity drainage (SAGD) to extract bitumen. Steam is injected in a well underground to heat the bitumen, which flows into a second, producer well, and then up to the surface.

But that’s not all that comes up. In addition to bitumen, water with a high saline content also enters the producer well as does condensed steam from the injection well.

Most in situ operators dispose of some saline water by pumping it into a disposal well underground (which are regulated), but Suncor doesn’t have a suitable disposal well nearby. So instead, the company devised ZLD, which treats the water to remove salts and recycles it to produce more injection steam and leaves only solids to be displosed. This way, more than 90 per cent of the injection steam required to run MacKay River is recycled continuously and Suncor has to draw very little water from underground aquifers.

Combining the ZLD system with MacKay River’s low “steam-to-oil ratio” (that is: less water is required for steaming than at other projects), means that for every barrel of heavy oil produced, Suncor uses about one-sixth of a barrel of new subsurface water.

The system also makes a difference to the bottom line. Expanding ZLD capacity at MacKay River has helped Suncor reach new production records (barrels per day). And, the company saves significant costs that would have been spent on third-party wastewater disposal.

Suncor’s goal in its oil sands operations – current and planned – is to use as little fresh water as possible in bitumen separation, generation of steam and cooling, and as process water during upgrading. The company is also committed to returning the water to the ecosystems at levels that meet or exceed regulatory standards.