Challenge

In the Powder River Basin of Wyoming, Petro-Canada needed to treat the produced water from a Coal Bed Methane (CBM) project to meet discharge regulations and minimize waste volumes.  CBM wells usually have to be dewatered to reduce pressure and allow methane gas to be released from the coal.  After this process, the water contains very high levels of sodium, amongst other contaminants, that must be removed before the water can be discharged into public water streams.  Often the wastewater from this process would go to a waste stream posing a second challenge—minimizing the volume of the waste stream to lower high costs incurred by deep well injection or hauling the waste off the site. 

Solution

Reverse osmosis (RO) and brine recovery reverse osmosis (BRRO) systems were the solution.  One issue was that Petro-Canada needed an immediate treatment solution, and the permanent RO-based system would not be installed and fully functional for about a year.  Siemens Water Technologies had another solution—they brought in a mobile reverse osmosis system containing media filters and RO to treat the water until the permanent system was completed less than a year later.

The permanent system consisted of iron removal, media filtration, chemical feeds, a primary RO system, a brine recovery RO system and a raw water blending system.  Iron removal and media filtration precede the primary RO system.  Media filtration removes iron and other suspended impurities that could clog the RO membranes.  The primary RO system removes approximately 95% of dissolved salts and produces 80 to 85% of treated water.  The remaining 15-20%, the brine, went to the reject stream for further treatment by the BRRO system to help minimize the volume of the reject stream.  With both RO systems and the allowed blending of the treated water with incoming raw water, total water recovery is between 95 to 98% and dissolved sodium in the influent stream went from being between 493 mg/l and 640 mg/l down to 325 mg/l to meet discharge requirements.

Results

The RO-based treatment system not only removes sodium from the water, but also achieves an overall higher water recovery rate of up to 98%.   This RO-based technology has helped Petro-Canada meet its permitting requirements while also proving to be a cost effective choice for the plant.  Along with the equipment supplied for this project, Siemens Water Technologies provides on-site service ensuring that the system is maintained and running at peak performance.