Water is pumped from thousands of shallow wells in the Powder River Basin of Wyoming to extract methane contained in coal bed seams, commonly referred to as coal bed methane or CBM. Over 2 barrels of water are pumped to produce a thousand cubic feet (MCF) of gas. The only environmental problem associated with the production of this clean burning domestic fuel is that the water's sodium bicarbonate content is so high that its discharge to the environment is harmful to both plant and animal life.
EMIT Water Discharge Technology LLC and Severn Trent Services, Inc. have teamed together to apply one of STS's technologies for the purification of this produced water. The Higgins Loop Continuous Ion Exchange (CIX) System utilizes cation resins in an efficient mode to remove sodium from the water and concentrate it into a very small brine stream for disposal. The process also reduces the water's bicarbonate content by evolving carbon dioxide gas from the low sodium treated water under slightly acidic pH conditions. Purified water is then neutralized with limestone. This step increases its calcium content and makes the water more suitable for use in irrigation, human consumption, ranching and for aquatic life in rivers and creeks.
The CIX process was first demonstrated in April, 2003 in a well field north of Sheridan, WY. Since then, EMIT has placed 15 more CIX Systems in operation in both Wyoming and Montana treating over 180,000 barrels per day of water. The technology has been accepted by both the gas producers and state regulators as the best available technology (BAT) and most economical process for CBM produced water treatment. This paper describes the reasons for produced water treatment, the purification process and the overall benefits to the industry and environment.