High efficiency reverse osmosis

High efficiency reverse osmosis (HERO) is a patented process (US Patent 5925255, Debasish Mukhopadhyay, 1999) originally developed to treat high silica water for the microelectronics industry. Its use has expanded to power and zero liquid discharge applications (see Chapter 15.4.3). Features of the process include ... 

The high efficiency reverse osmosis (HERO ) process is used for enhanced rejection of silica and boron in SWRO and HPW applications [30]. The process is capable of high rejection of silica, TOC and boron with RO. Further, organic cleaning is minimised at high pH levels, akin to operating the RO unit in a continuous cleaning mode. 

The High Efficiency Reverse Osmosis, or HERO (HERO is a trademark of Debasish Mukhopadhyay) takes advantage of the elevated concentrations of silicates at very high pH (Figure 7.5) and removes metals as part of the HERO process to eliminate the potential for forming metals silicates at high pH on the RO membranes. See Chapter 16.5 for more on the HERO process. 

Reverse osmosis requires good pretreatment to prevent membrane fouling and loss of performance. Because it is seldom better than 60 to 70% efficient, there is a relatively high cost for pumping and discharging the additional supply water consumed. Nevertheless, it is good as a bulk water roughing process for purification. 

It is the rate of separation rather than the efficiency of salt retention that is the primary practical issue in the development of reverse osmosis desalination. In addition to a variety of other factors, the rate of reverse osmotic flow depends on the excess pressure across the membrane. Therefore the problem of rapid flow is tied into the technology of developing membranes capable of withstanding high pressures. The osmotic pressure of sea water at 25 °C is about 25 atm. This means that no reverse osmosis will occur until the applied pressure exceeds this value. This corresponds to a water column about 840-ft high at this temperature. 

In nuclear industry ultrafiltration was applied in the pretreatment stage before reverse osmosis that needs removal of potential foulants from feed streams. Very often ultrafiltration is combined with precipitation or complexation. Small ions bound by macromolecular chelating agent form complexes, which are retained by UF membrane. Such an enhanced ultrafiltration becomes an efficient separation process with high decontamination factors, sometimes compared with those... 

Ethanol produced by fermentation is conventionally dehydrated by distillation, an inefficient process that consumes energy equivalent to a large fraction of the energy content of the product ethanol.(X) Reverse osmosis (RO) has been considered before for ethanol-water separation because of its inherent energy efficiency. However, a difficulty encountered in using RO is the high osmotic pressures associated with concentrated ethanol solutions. For example, the osmotic pressure of a 15-volX ethanol solution is about 960 psi, and that of a 50-volX solution is about 3700 psi.(2,) Because most... 

---