Evaluation of the Effectiveness of Zeolite In Mitigating Impacts of Coalbed Natural Gas (CBNG) Co-Produced Water On Soil.

A research study evaluated the potential impacts of high sodicity CBNG water on a soil’s hydraulic characteristics and chemical properties. The effectiveness of Bear River (BR) zeolite for mitigating the soil property effects of high sodicity water was also evaluated. A batch adsorption isotherm study revealed that adsorption of sodium (Na⁺) was impacted by the type of anions associated with Na⁺, indicating that bicarbonate (HCO₃^-) had a greater influence on Na⁺ adsorption compared to Cl^- ions. Fitting the data to Langmuir and Freundlich models revealed that the coefficients of Na⁺ adsorption were higher for HCO₃^- compared with Cl^-. An adsorption kinetics study indicated Na⁺ retention by BR-zeolite was an inverse function of particle size. The CBNG water sodium adsorption ratio (SAR) was also reduced from 30 to below 10 (mol/m³)^1/2 in the first 30 minutes of batch reaction. Both a laboratory column study and a field study utilizing a falling head permeameter infiltration test indicated that hydraulic conductivity was not impacted as significantly when the CBNG water leached through the BR-zeolite. An analysis of influent and effluent water from the columns study and the post-treatment analysis of saturated paste extracts from soils collected from the bottom of 1.8 meter deep boreholes and depths of 0-5, 5-15, 15-30, 55-65, 95-105 cm and below, revealed reduced soil SAR and electrical conductivity (EC) for columns and boreholes containing BR-zeolite. By reducing the potential impacts of sodic CBNG waters on the physicochemical properties of soil and groundwater, it is possible that Ca²⁺ and Mg²⁺ rich zeolites lining infiltrated containment ponds can enhance the beneficial use of co-produced water for groundwater recharge for wetlands enhancement and other possible uses.