Investigation of Membrane Fouling and Cleaning in Direct Contact Membrane Distillation of Municipal Wastewater

Municipal wastewater discharge to the environment is generally subject to regulations established under the Clean Water Act. Though the water is highly treated it is not suitable for human consumption. Increased interest in water reuse for potable supply introduces concern about trace constituents present in their water, such as pharmaceuticals and endocrine disruptors. Current treatment processes, such as reverse osmosis, are used to remove many of these compounds, but is expensive and energy intensive. The rise of interest in potable water reuse may cause consumers to be concerned about trace constituents present in their water and would require additional treatment. Membrane distillation may be applicable in some circumstances to treat the effluent from municipal wastewater treatment plants with a low grade heat source for direct potable reuse. This project investigated the chemical cleaning efficiency of ethylenediaminetetraacetic acid (EDTA) on membrane wastewater effluent fouling for direct contact membrane distillation (DCMD) to help assist wastewater reuse become a reality. A laboratory scale DCMD system was designed and constructed including a warm feed loop and cold permeate loop to utilize a flat sheet, crossflow membrane cell. Treated wastewater effluent collected from the Albuquerque Bernalillo County Water Utility Authority (ABCWUA) Southside Water Reclamation Plant (SWRP) was used as the feed solution. The performance of the MD system was tested and evaluated using parameters including flow rate, feed and permeate temperature, feed water quality, permeate flux, membrane area, cross flow velocity, and membrane type and pore size. An (EDTA) cleaning solution was used to clean a 0.2μm polypropylene (PP) membrane that had reached a 50% flux decline due to wastewater effluent fouling. The cleaning process was repeated on the membrane three times to determine the effectiveness of removing wastewater effluent fouling by permeate flux recovery. Overall system data collection and analysis determined the influences of system parameters on permeate flux, constituent rejection, membrane fouling rate, and a membrane chemical cleaning. Results produced from this study give a better understanding of the membrane distillation process, and membrane cleaning when treating municipal wastewater effluent, and gives potential to DCMD for becoming an optional process for potable water reuse.National Science Foundation, Grant #1345169Civil EngineeringMastersUniversity of New Mexico. Dept. of Civil EngineeringHowe, KerryThomson, BruceSchuler, Andre