Interrelationships Between Flux, Membrane Properties, and Soil Water Transport in a Subsurface Pervaporation Irrigation System

Abstract

Oil and natural gas-produced waters are by-products of energy development that present unique challenges to the energy industry and impacted landowners. Conventionally, produced waters are typically saline and therefore must be desalinated to some extent before beneficial reuse. Subsurface pervaporation irrigation combines desalination with beneficial reuse in the form of crop irrigation. This investigation studied factors governing water flux for two membranes, one polyether ester (PEE) and one cellulose triacetate (CTA), for use in subsurface pervaporation irrigation. Water flux was determined to be a function of membrane properties (thickness, hydrophilicity) and environmental variables (vapor pressure gradient, soil texture, soil clay content). Specific water fluxes ranged from a maximum of 6.77×10−2 L/[m2·day·Pa] for CTA membranes to a minimum of 7.97×10−3 L/[m2·day·Pa] for PEE membranes. Fluxes increased as water vapor pressure in the soil adjacent to the membrane decreased. Total soil water potential and its specific components, matric potential and osmotic potential, influenced flux. Clayey and peaty soils have a lower matric potential than sand for the same soil water content, which translated to a lower vapor pressure and hence higher flux for clayey/peaty soils.