Using integrated electrodialysis and RO hybrid system to remediate and reclaim perchlorate-contaminated groundwater

Abstract

Perchlorate (ClO4−) is a highly oxidizing and water soluble chemical. In this study, a hybrid electrodialysis reversal and reverse osmosis process (EDR + RO) was designed to remediate and reclaim perchlorate-contaminated groundwater. The EDR tests were conducted using a laboratory-scale equipment with seven pairs of ion-selective membranes and a total membrane area of 352 cm2. Up to 95% of perchlorate could be removed in 2.5 h of operation with a voltage of 40 V. The effluent perchlorate concentration dropped to below 0.02 mg/L after the two-stage treatment (EDR followed by RO). Bimetallic nanoparticles Fe0/Al0 (nZVI-coated nZV aluminum) were applied to reduce perchlorate via chemical reduction. Approximately 30.8% of perchlorate could be removed by Fe0/Al0 reduction. Strong acidic functional group (SO3H) on the EDR cation exchange membrane was electrolyzed, which resulted in the accumulation of sulfur content on the ion-exchange membrane. Results from the 3-D excitation-emission fluorescence matrix (EEFM) analyses show that the most proportion of organic matters in groundwater were type II and type IV that are aromatic protein (AP) and soluble microbial by-product-like (SMP) chemicals. The system could electrolyze perchlorate and generate hydrochloric acid (HCl), which could inhibit the hydroxide production and minimize the fouling on the RO membrane.