Membrane Process Offers Improved Water Recovery
By Hu Fleming, Ph.D., and Riad Al-Samadi, Ph.D.
In the United States, technical and economic challenges associated with the disposal of high-salinity effluents and reverse osmosis (RO) membrane plant reject water continues to undermine the viability of commercial and industrial projects in arid southern states, which suffer from depleting water reserves (1). As the dissolved ions and other constituents become more concentrated, the reduced volume of RO reject streams become more difficult to dispose of in an economical manner since these rejects cannot be discharged to receiving waters, or comply with local municipality permit requirements. Dependence on costly and energy-intensive brine concentrators and crystallizers to dispose of these rejects (i.e., in some cases up to 25% to 30% of the influent raw water volume) and to achieve zero liquid discharge (ZLD) is technically challenging, and in most cases not economically viable (2). There is a need to address water shortages, maximize fresh water utilization, and minimize the volume of waste (reject) streams to enable their economical disposal via evaporation ponds or low-cost spray dryers.
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