Reverse Osmosis

Abstract

Reverse osmosis is a membrane‐based separation technology, which was developed in the late 1950s and early 1960s, with rapid advancements in the technology through the 1980s. A highly effective and cost‐efficient technology, reverse osmosis is used industrially for desalination of seawater and brackish water, wastewater recovery and reuse, municipal drinking water treatment, and other applications. Membrane materials and types of modules used in reverse osmosis, as well as theoretical and operational aspects, general design considerations, and economics are reviewed in this article. A discussion of membrane transport theory, flux‐limiting conditions caused by concentration polarization, and membrane fouling is also included.

Long-Term Stability of Low-Pressure Reverse Osmosis (RO) Membrane Operation—A Pilot Scale Study

“…where P is operating pressure, ΔP is differential pressure, Pp is permeate pressure, and π is osmotic pressure derived from the logarithmic mean concentration of feed and concentrate [7][8][9]19,23,39]. The feed water in the pilot test was fed into the two parallel pressure vessels of the pilot RO system after passing the conventional coagulation, sedimentation, and fine fibrous 5-μm microfilter filtration sequentially.…”

“…Considering the general guidelines for the RO feed water qualities, the TOC, SDI, and turbidity values of the raw water are over the maximum allowable ranges [7,8,39]. After a 646 h operation, the retentate of each vessel was recycled to the feed water to generate a higher-fouling-potential feed water condition (Figure 1), and as shown in Table 4, the TOC, SDI, and turbidity noticeably increased after the recycling of the retentate.…”

“…However, the RO process is still subject to numerous demands including the reduction of the operation and maintenance costs [1][2][3][4][5][6][7][8][9][10], prolonging the membrane lifetime [7][8][9][10][11][12][13][14][15][16][17], and advancing the membrane module and system configuration designs [7,8,18]. The development of a low-pressure (higher flow rate) RO membrane could accomplish some of these demands.…”

“…Low-pressure RO elements that can be operated at low pressures such as 7.5 bar have been developed for energy saving [19]. Furthermore, ultra-low-pressure RO elements that can be used at much lower operating pressures such as 3 bar to 5 bar were also developed [8,20,21]. With the advances in the membrane performance, the portion of RO element cost in RO systems has simultaneously decreased [7][8][9]19].…”

“…Furthermore, ultra-low-pressure RO elements that can be used at much lower operating pressures such as 3 bar to 5 bar were also developed [8,20,21]. With the advances in the membrane performance, the portion of RO element cost in RO systems has simultaneously decreased [7][8][9]19]. However, despite the recent noticeable progress in the membrane performance, the membrane still suffers from the membrane fouling that is an accumulation of various contaminants on the membrane surface.…”