Potential Utilization of Natural Zeolites for Treating Coalbed Natural Gas (cbng) Produced Waters Studies

Fast development of the coalbed natural gas (CBNG) industry in many parts of the western U.S. has resulted in the co-production of potentially salinesodic waters, hereafter referred to as CBNG water. Management of CBNG water is a major environmental challenge because of its quantity and quality. In this study, the potential utilization of calcium (Ca)-rich natural zeolites were examined for removal of sodium (Na) from CBNG waters. Zeolite samples examined were from the St. Cloud (ST) zeolite mine in Winston, NM and the Bear River (BR) zeolite mine in Preston, ID. The zeolite materials were used in adsorption kinetic/isotherm studies and column experiments. A surrogate CBNG water that simulated the water chemistry of CBNG waters was used in the various studies described herein. Results indicated that a Langmuir model fit the adsorption data well. The maximum adsorption capacities from the adsorption isotherms for ST-Zeolite and BR-Zeolite were 9.6 and 12.3 (mg/g), respectively, accounting for approximately 38% and 39% of their measured CEC values. Column studies indicated that a metric tonne (1000 kg) of ST-zeolite and BRzeolite can be used to treat 16,000 and 60,000 liters of CBNG water, respectively, in order to lower the sodium adsorption ratio (SAR, mmol L) of the simulated CBNG water from 30 mmol L to an acceptable level of 10 mmol L. Based on the results of this study Na removal with zeolite appears to be a cost-effective water treatment technology for maximizing the beneficial use of poor-quality CBNG water. Ongoing studies are evaluating water treatment techniques involving the direct application of zeolite to CBNG waters and development of a field scale prototype. Additional