Self-Sustaining Produced Water Treatment for Concurrent Renewable Energy Production, Desalination and Organic Removal
P Xu, Z Stoll
Management of produced water generated during oil and natural gas exploration and production is a significant challenge. Produced water contains contaminants such as petroleum hydrocarbons, salts, and chemical additives. The water is considered hazardous waste and must be treated or disposed safely. In this project we developed an innovative microbial capacitive deionization cell (MCDC) to simultaneously remove organic substances and salts from produced water so the treated water can be potentially recycled and reused. Moreover, compared to other energy intensive systems, MCDC uses bacteria to convert biodegradable pollutants into direct electricity, which offsets operation energy use or supplies additional energy for other systems. In this study the MCDC was comprised of three chambers – anode, desalination, and cathode, each with internal volumes of 23, 12, and 27 mL, respectively. Produced water treated by the MCDC had total dissolved solids concentration of 15,900 mg/L and dissolved organic carbon (DOC) concentration of 230 mg/L. Microbial degradation of organic compounds in the anode generated an electric potential that drove the desalination of produced water. Sorption and biodegradation resulted in a combined organic removal rate of 6.4 mg DOC per hour in the reactor, and the MCDC removed 36 mg salt per gram of carbon electrode per hour from produced water. This study demonstrated that MCDC could be used to combine organic degradation and desalination of contaminated water without external energy input.
microbial fuel cell; desalination; capacitive deionization; produced water treatment; organic removal; bioelectrochemical processes