WITHDRAWN: Concentrate Management of Spent Geothermal Water Treated with Two- Step Membrane Processes for Agricultural Irrigation

Abstract

This study examines a two-step membrane treatment to improve water quality by targeting electrical conductivity in reverse osmosis (RO) concentrate from spent geothermal water. The process involves RO treatment followed by electrodialysis reversal (EDR). Water samples were collected during different seasons to assess quality under varying conditions.Following the initial treatment by XLE-RO membrane test system, the large-pilot membrane (LPM-RO) concentrate achieved salt rejection of 98.6%, while the mini-pilot membrane (MPM-RO) concentrate achieved salt rejection of 95.6%. Conductivity values were 48.6µS/cm for LPM-RO and 226µS/cm for MPM-RO concentrate. Further passing the product water obtained from XLE-RO membrane through the EDR system improved overall product water quality. Treated LPM-RO product water had conductivities of 3.71µS/cm (5V) and 2.36µS/cm (10V). For MPM-RO product water, conductivities were 11.98µS/cm (5V) and 2.64µS/cm (10V). In this study, an additional experiment investigated the EDR treatment of RO concentrate without undergoing initial RO pretreatment. After the experiment, although the salt rejection reached 97.65%, it was observed that the product water quality at the end of the 90-minute treatment was 74.6µS/cm with lower quality as compared to when the RO concentrate underwent initial RO pre-treatment. Hence, the combination of RO-EDR can be successfully utilized to treat geothermal water concentrate for better quality which could be utilized in irrigation. This two-step membrane treatment shows potential for higher-quality water reclamation for various processes.