BTEX removal from produced water using surfactant-modified zeolite

Produced water (water generated during recovery of petroleum) contains large amounts of various hazardous organic compounds such as benzene, toluene, ethylbenzene, and xylenes (BTEX). With increasing regulations governing disposal of this water, low-cost treatment options are necessary. This study evaluated the effectiveness of surfactant-modified zeolite (SMZ) for removal of BTEX from produced water. The long-term effectiveness of SMZ for BTEX removal was investigated along with changes in sorption properties with long-term use. The results of these investigations show that SMZ completely removes BTEX from produced water up to a compound-specific capacity, and that SMZ can be regenerated via air sparging without loss of sorption capacity. The BTEX mobility in laboratory columns of SMZ was in the order of decreasing water solubility and increasing K(ow). The most soluble compound, benzene, began to elute at 8 pore volumes (PV), while the least soluble compounds, ethylbenzene. and xylenes, began to,elute at 50 PV. After treating 4,500 PVs of water in the column system over 10 sorption/regeneration cycles, no significant reduction in sorption capacity of the SMZ for BTEX was observed. The mean K(d)s. determined in these column experiments ranked from 18.3 L/kg for benzene to 95.0 L/kg for p- and m-xylene. Laboratory, columns were upscaled to create a field-scale SMZ treatment system. The field-scale system was tested at a natural gas produced-water treatment facility near Wamsutter, Wyo. We observed even greater sorption of BTEX in the field column than predicted, from the laboratory results. In the field column, initial benzene breakthrough occurred at 10 PV and toluene breakthrough began at 15 PV, and no breakthrough of ethylbenzene or xylenes occurred throughout the 80 PV experiment. The field and laboratory results, along with the low price of SMZ (about $460 per metric t), suggest that SMZ has a potential role in a cost-effective produced water treatment system.