(706d) Magnetically-Activated Membranes for Wastewater Treatment

Filtration membranes, whose filtration properties are controllable via application of an external magnetic field, have been developed.  Poly(2-hydroxy ethyl methacrylate) (polyHEMA) chains are grafted onto the surface of commercially available nanofiltration membranes.  Superparamagnetic nanoparticles are then covalently bound to the end of the polyHEMA chains.  When a magnetic field is applied, the nanoparticles will experience a force as they align with the direction of the magnetic field.  When place in an alternating magnetic field, the chains quickly align back-and-forth over the surface of the membrane.  This motion creates small areas of micro-mixing directly above the membrane surface, decreasing the severity of concentration polarization.  It is argued that this effect should reduce membrane fouling due to colloidal foulants.

Oily wastewaters were treated using these responsive membranes.  The wastewaters used were oily produced water, a byproduct of oil and gas operations, from coal bed methane wells in Colorado and Wyoming.  The severity of fouling, shown by a reduction in flux decline and improved rejection, is reduced by the micromixing in an alternating field.  Additionally, the membranes are more easily cleaned, and the modified membranes recovered a greater fraction of their original flux after cleaning.

It is believed that the filtered produced water permeate could be suitable for irrigation use without the addition of chemicals.  Produced water permeate were applied to soil columns to test the effect of this hypothetical irrigation water on soil properties.  The permeate was then used to water a variety of seed currently grown in Colorado and Wyoming.  These tests indicate that the filtered produced water permeate could be suitable as an irrigation water if the proper soil and crop were chosen.