Characterization of transport through polymers for fracking fluid treatment and organic acid concentration in extractive membrane bioreactors

Abstract

BACKGROUND: The water-intensive practice of hydraulic fracturing produces wastewater containing a variable matrix of organic and inorganic compounds, including ions and ionizable organic compounds. Extractive membrane bioreactors (EMBs) operating with tailored polymer membranes can selectively sequester and/or transport these solutes for biological treatment. Four grades of Hytrel™ tubing were compared for their suitability in EMB systems, based on the polymers' thermodynamic affinity for solutes and their ability to transport or speciate ionic wastewater constituents. RESULTS:Of the four Hytrel™ grades compared, high water content types (30% and 54% equilibrated water content) facilitated the transport of ionic species through the tubing, with all monovalent species being transported through both high-water content grades, and lack of transport through the low-water content tubing (3% and 5%). Undissociated organic acids were transported through all tubing types and dissociated acids were able to permeate only high-water content grades. Using this differential ability to transport/not transport an organic acid depending on its dissociation state, a low-water content Hytrel™ grade of tubing was able to concentrate a dilute butyric acid solution by 220% after 48 h. CONCLUSION: The use of polymeric tubing for EMB applications for the treatment of hydraulic fracturing wastewater requires knowledge of both solute affinity and water content for complex waste streams, both of which affect the capability to transport organic and ionic species.