Water quality of shale gas produced water greatly influences the performance of membrane distillation

Shale gas is abundant worldwide and has a smaller carbon footprint than conventional coal. However, exploitation of shale gas produces a large amount of hydraulic fracturing wastewater, which hurts the ecological environment. Effective treatment of shale gas produced water (SGPW) is a great challenge and membrane distillation (MD) which is not restricted by salinity is a hot topic in dealing with this wastewater. This paper focused on the influence of feed water quality on performance of direct contact MD by adjusting pH and pretreating. By analyzing MD permeate, controlling the feed water non-alkalinity facilitated MD treatment of SGPW and acidic condition greatly hindered the cross -membrane mass transfer of ammonia nitrogen. Among the traditional pretreatment methods, aluminum coagulant removed 99% of turbidity and exhibited the best superiority in mitigating membrane fouling, whose final flux was 2.2 times the raw SGPW. Dual coagulation and zeolite adsorption reduced ammonia nitrogen by about 50 % and 95 %, whose final permeate conductivities were about 65 % and 62 % of the untreated, respectively. Analyses of attenuated total reflection fourier transform infrared and scanning electron microscope equipped with an energy dispersive spectroscopy confirmed the reduction in membrane fouling after pretreatment of feed water. This study provides guidance for treatment of SGPW using MD.