(339g) Evaluation of Integrated Electrocoagulation-Microfiltration and Direct Contact Membrane Distillation Processes for Produced Water Treatment

Treating the wastewater generated from hydraulic fracturing operations is challenging due to the presence of high salinity (total dissolved solids (TDS)), toxic organic & inorganic compounds, oil & grease, and naturally occurring radioactive materials. In addition, the presence of surfactants that can adsorb onto the membrane surface means fouling is a major concern. Thus, pre-treatment of the feed is essential prior to membrane distillation (MD) which is an emerging technology for treating high salinity brines. Here a combined electrocoagulation, microfiltration and membrane distillation process has been developed to treat oil and gas produced and flow back waters from hydraulic fracturing operations.

A continuous electrocoagulation cell has been designed to flocculate the organic matter present in the raw produced water. A range of microfiltration membranes (polymeric, metal) were used to remove the flocs formed during the electrocoagulation. The permeate from the microfiltration membrane was treated further by direct contact membrane distillation (DCMD). Different types of membranes with different surface properties were investigated for DCMD. In this work, we aimed to demonstrate the feasibility of an integrated EC-MF-DCMD system for water recovery from high salinity produced waters. During EC, a high removal efficiency of total organic carbon (48.4%) was obtained by using 6 aluminium plates with bipolar configuration at 9.5 A for 20 min. Keeping the feed tank temperature at 40 ^oC, while the temperature inside the model is maintained at 60 ^oC can effectively suppress crystallization on the membrane surface, which can significantly decrease scaling. 50% water recovery was obtained using commercial membranes over two DCMD cycles. However, suppressing fouling by organic compounds, especially surfactants due to formation of micelles and bilayers, is essential to maximize the lifetime of the DCMD membrane.