It is globally urgent to address the dwindling clean water supply for human health and nutrition, and energy generation reasons (water/energy/food nexus). The shortage is caused by population growth, pollution and climate change (local drought and contaminated runoffs from flooding). Contaminants include hormones, pharmaceuticals, pesticides, personal care products and industrial chemicals that are detrimental even at low concentrations. Although many sustainable water purification technologies are available, most require complex equipment or chemicals and are costly to operate with a high energy consumption. Furthermore, standards are still evolving toward more stringent water quality specifications and a limited sludge discharge, which support the development of alternatives. Membrane filtration and reclamation, the next generation technology, is selective, operates on a continuous basis with little or without chemicals, occupies little space, scales up easily and consumes little energy. The Hawaii Natural Energy Institute will evaluate the potential of fuel cell membrane materials and designs to further reduce energy consumption and minimize the impact of fouling for a longer filtration unit life.

Model water compositions will be produced by dissolving a representative species from three different contaminant classes (gases, organics and ions) into purified water and using concentrations typical of applications. The wastewaters will subsequently be injected in one of the two compartments of a fuel cell and in a single pass mode to maintain exposure conditions at a constant level. The conventional fuel cell membrane/electrode assembly structure and operating conditions will be modified to selectively favor the transport of water through the membrane. The water permeating through the membrane (cross-flow arrangement) will be collected for a specific duration and analyzed to calculate the selectivity for the different species (titration, total organic carbon, ionic conductivity, ion chromatography, gas chromatography/mass spectroscopy) and water permeability, key water purification metrics. Tests will be completed with two different membrane/electrode assemblies to highlight the structure change impact on selectivity. Experimental data will be used to define a development plan if metrics are promising in comparison to competing technologies such as reverse and forward osmosis.

Point Person: Jean St-Pierre

 

Membrane Filtration Spectrum

Schematic illustration of membrane filtration spectrum. Reverse osmosis, nanofiltration, ultrafiltration, microfiltration, and conventional particle filtration differ principally in the average pore diameter of the membranes. Reverse osmosis membranes are so dense that the pores are considered as non-porous. Courtesy: Environmental Science: Water Research and Technology, volume 2 (2016) page 17.