Abstract
Reverse osmosis (RO) elements operating at a low pressure (LP) or a low energy (LE) are generally called “LPRO” or “LERO”, and the nomenclature “LP” and “LE” are convertible due to the interrelated features of the pressure and the energy in the RO process. Not only can LPRO be operated at lower pressures, which enables energy saving, but also at the standard operating pressure with an enhanced permeate flux. In this study, the feasibility of the LPRO element was evaluated in the face of high fouling potential feed water. The commercially available standard RO and LPRO were chosen, and the membrane properties including the fouling susceptibility and the surface characteristics were thoroughly evaluated. The variations of various performance parameters were monitored during an 872 h operation in a pilot system, which was operated in a constant flux mode. Then, the used membranes were analyzed to further verify the fouling load localization and the fouling intensities. The average flux variation of the individual RO elements in a vessel and the economic feasibility of LPRO were also evaluated through a simulation study using an RO system design software. This study showed that the localization of fouling load within a pressure vessel of an LPRO system caused about 20% higher flux decline and almost 2-times higher salt passage than those of a standard RO membrane system. Furthermore, the simulation study predicted that average operating pressure difference ratio (%) between two RO membranes decreased from 24.4% to 17.8% and a substantial quantity of LPRO elements (83.3%) must be replaced to meet the designated water criteria only after 2 years’ operation.
Highlights
Reverse osmosis (RO) is a representative demineralization process for which a semipermeable membrane is adopted to remove the dissolved substances from a solution
The feasibility of low-pressure RO elements was evaluated through the adoption of feed water with a high fouling potential and two types of commercial RO
The feasibility of low-pressure RO elements was evaluated through the adoption of feed water with a high fouling potential and two types of commercial RO elements with different permeate flow rates
Summary
Reverse osmosis (RO) is a representative demineralization process for which a semipermeable membrane is adopted to remove the dissolved substances from a solution. Liquid and only the marginal portion of some ions can pass to the permeate side through a semipermeable membrane, but the majority of the dissolved materials are rejected. The RO membrane process has been regarded as one of the most economically advantageous separation technologies for both seawater desalination and the purification of various water resources contaminated with pesticides, pharmaceuticals, heavy metals, or other emerging micropollutants. Along with food and beverage processing, the RO process can be used for recycling wastewater and reclaiming highly valuable resources from the various industrial waste streams. The design and operation of the RO process are relatively simple compared with the other traditional separation processes. The simultaneous achievement of the separation and concentration for diverse compounds is another merit of the RO process
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