Removal of organic compounds from shale gas fracturing flowback water by an integrated electrocoagulation and electro-peroxone process

Abstract This study investigated the removal of organic compounds from shale gas fracturing flowback water (FFW) by an integrated electro-coagulation and electro-peroxone (EC-EP) process in a divided electrochemical reactor. During the EC-EP process, electricity was efficiently utilized to produce both aluminum ion (Al3+) from electrochemical oxidation of an aluminum anode in the anodic compartment and hydrogen peroxide (H2O2) from oxygen reduction at a carbon-based cathode in the cathodic compartment. The in-situ generated H2O2 then reacted with ozone (O3) sparged in the cathodic compartment to produce hydroxyl radicals (•OH) for pollutant oxidation. The results showed that by sequentially treating the selected FFW by the EC and EP process in the anodic and cathodic compartment for 30 min, respectively, the EC-EP process effectively removed ∼95% of total organic carbon (TOC) from the FFW, meeting the wastewater discharge standard for TOC (≤ 30 mg/L) with a low specific energy consumption of 0.11–0.21 kWh/g TOC removed. In contrast, individual EC and EP process, as well as the previously investigated ECP process that combined the EC and EP process in an undivided reactor, removed only ∼76%, 32%, and 80% TOC from the FFW under similar reaction conditions, and thus could not meet the wastewater discharge standard. These results demonstrate that the EC-EP process successfully integrates the merit of the EC and EP process and may thus provide a cost-effective way to remove organic compounds for FFW disposal and reuses.