HERO Process

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 HERO process includes the following process steps  

In many cases, additional pretreatment is required prior to the HERO process. Additional pretreatment can include cold lime softening, sodium softening, and ultrafiltration or microfiltration. These pretreatment unit operations are required when the total hardness is very high and/or the concentration of suspended solids is high. 

High efficiency RO is not practical for every-day RO applications due to the relative complexity and high capital and operating cost involved. However, for difficult feed streams that require high recovery, HERO is well suited. Advantages of HERO over conventional RO for these applications include  

Limitations of HERO for ZLD include the number of unit operations required for treatment and the need for significant chemical application and sludge disposal. Other limitations with the HERO 

Very high recovery, including high silica feed water Less space required due to higher water flux and smaller RO (HERO systems typically operate at 25-30 gfd)  

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Colloidal silica can be removed or reduced in RO feed water using coagulation/clarification (see Chapter 8.1.1). Soluble silica is typically dealt with using high pH, elevated temperature, antisealants (see Chapter 8.2.3), or the HERO process. Sometimes, the recovery of the RO system is adjusted to minimize the potential for forming silica scale. 

Figure 16.20 Process flow diagram of a typical HERO process.

High efficiency RO is often used in zero liquid discharge (ZLD) applications. The HERO process is used prior to the thermal equipment to reduce the size and energy required by the thermal system. In many cases, the brine concentrator can be eliminated entirely, such that the concentrate from the HERO process feeds directly to the crystallizer. 

Suppliers of the HERO process under license include GE and AquaTech. 

Outotec from Gemnany are suppliers of technology for large size (5,000 tonnes per day (TPD)) sulfuric acid plants and have innovated processes for sulfonation. See Appendix. Outotec have developed the Hero process which should also be considered for sulfonations. 

Innovative heat recovery systems developed by Monsanto known as HRS and by Outotec known as Hero Process or Alfa can be considered. 

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 central premise of the HERO process is the removal of all hardness in RO feed water so that RO can be operated at a high pH where silica is highly soluble. Opex is, however, 60—70% higher than RO alone. The HERO technology consists of three basic processes operating in series ... 

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. 

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