Marcellus Shale Produced Water Treatment by Direct Contact Membrane Distillation with Acrylic Copolymer Membranes

摘要

Membrane distillation (MD) is a promising treatment solution that can provide the oil and gas industry an efficient and cost effective desalination treatment method for flowback and produced waters. This will allow the industry to look beyond deep well injection and reuse as the chief water disposal management practices. A potential setback of MD treatment for oil and gas wastewater applications is that volatile organic compounds can degrade the hydrophobicity of membranes most commonly used in MD, which would allow salt breakthrough into the permeate. To overcome this setback, an acrylic copolymer hydrophobic membrane with oleophobic properties was selected for MD treatment of flowback and produced waters using a direct contact membrane distillation module. udExperimental runs with this module were conducted with pure sodium chloride solutions as well as with synthetic and actual flowback/produced waters at different TDS concentrations. The acrylic copolymer membrane had a permeate flux of 30.1 kg/m2hr for 3.5% NaCl solution which is comparable to other hydrophobic membranes that have been widely accepted by the MD industry. There was little observable difference between the permeate flux measured using pure sodium chloride, synthetic flowback, and actual flowback when comparing equivalent percent salt concentrations. The permeate flux decreased with TDS increase. The permeate flux increased as the temperature difference between the hot feed and cold permeate side decreased for all waters tested. Both 0.2 and 0.45µm nominal pore size acrylic copolymer membranes were studied with the 0.45 µm performing marginally better for flux production while the 0.2 µm membrane seemed to be more effectively rinsed. For all experiments conducted there were no signs of pore wetting and ionic breakthrough and the initial longevity test results are positive indicating that MD treatment for oil and gas wastewater applications may be viable.