Desalination of Hydraulic Fracturing Waste Water with Multiple Cathode Chambers in the Microbial Fuel Cell
Hydraulic fracturing waste water contains high level of total dissolved salts which is about five times more salty than the sea water. Hence it is important to treat the waste water before recycling it for use in hydraulic fracturing or safety discharging it into disposal facilities. There are number of desalination methods available such as nanocomposite membrane, semi batch reverse osmosis and ion concentration polarization. But integrating these technologies with hydraulic fracturing operations are considered very challenging. In this study multiple cathode chambers in the Microbial Fuel Cell (MFC) configuration was developed and used to treat the salty hydraulic fracturing waste water in the cathode chambers and oil waste in the anode chamber. Also salt absorption by polymer was tested for use in the bridge. The two chamber MFC was tested with the cathode salt concentration of 35 g/L and 175 g/L and the desalination rates were 52 mg/L/hour and 115 mg/L/hour respectively. In the multiple cathode chamber MFC different salt concentrations were tested in the four cathode chambers and the maximum total desalination rate was 2.93 g/L/hour within three hours of operation with the polyacrylamide bridge. Hence the multi chamber MFC was more effective in the rate of desalination of hydraulic fracturing waste water compared to the two chamber MFC. Also bio-surfactant was produced in the anode chamber and was quantified by measuring the changes in the surface tension.