HERO Process

HERO is a registered trade marked acronym for High Efficiency Reverse Osmosis. The internationally patented HERO process involves operating an RO system(s) at the highest pH level acceptable to RO element manufacturers (typically a pH level of up to 11 in RO reject stream) in conjunction with hardness removal, alkalinity removal, and/or dissolved gas (CO2) removal. Any combination of two or more technologies that remove hardness, alkalinity, or dissolved gas (CO2), while operating at a pH greater than 8.5 in front of an RO system, constitutes the patented HERO process.

As part of the HEROTM process, feed water is pretreated to the RO system(s) with either Weak Acid Cation (WAC) or Strong Acid Cation (SAC) ion exchangers to remove virtually all hardness causing polyvalent Cations – such as calcium, magnesium, barium, strontium, aluminum, iron, manganese, etc. The next step involves some form of degasification – such as Forced Draft Degasifier (FDG) or Gas Transfer Membrane system (GTM) – to reduce the carbon dioxide present in the feed water. Following degasification, the feed water is pH adjusted above 8.5 prior to Reverse Osmosis. Therefore, a typical HERO process will consist of: WAC or SAC (for hardness and alkalinity removal), FDG or GTM (for dissolved gas removal), feed water pH adjustment above 8.5, followed by single-pass or two-pass Reverse Osmosis (for TDS reduction).

Higher RO Production and Water Efficiency

The removal of all potential scale forming constituents via the pretreatment scheme allows the RO to operate at high recoveries and flux rates. The HERO process allows the RO system to reliably operate 2X flux rates above conventional RO, up to 30 GFD or more, and an overall water recovery ratio of 90% to 98% – thereby reducing both the cost of ownership (less membrane to periodically replace, less feed water to treat and pump, less feed water to purchase, less reject water to dispose of, etc.), as well as the physical size of the equipment (e.g., space savings).

Higher Boron, Silica, Fluoride, Cyanide, and TOC Rejection

One of the many benefits of operating an RO system at or very near a pH of 11 is the significant increase in the rejection of weakly ionized Anions, such as organics, silica, boron, cyanide and fluoride. Since humic/fulvic acid derivatives (TOC), silicic acid, hydrofluoric acid and boric acid are all relatively weak acids, at very high operating pH levels these acids will dissociate to a much greater extent compared to conventional RO operating conditions (i.e., lower pH). Furthermore, negatively charged strongly ionized species are also better rejected at high pH levels resulting in a lower RO product water ionic level. For example boric acid is a very weak acid with an equilibrium constant (pKa) value of 9.2. This means that at a pH of 9.2, approximately half of the boron is present in its dissociated borate form. At a pH lower than 8.2, about 90% of the boron is present in its un-dissociated form (boric acid). At a pH of 11, it is approaching 99% in the dissociated form (borate) and readily rejected by RO. The same increase in RO rejection can be said for silica and fluoride as well.

Elimination of Bio-Fouling

The HERO process operates very near a pH of 11. At this pH level, the lipid casing surrounding the bacteria is dissolved thereby killing the microorganism. Therefore, the HEROTM process is not prone to bio fouling – as the RO system essentially operates in a constant state of ‘RO cleaning’.

Ability to Operate on High Silica Feed Waters

The HERO process can reliably operate at silica levels in the RO reject stream up to 2,000 ppm, or higher. At a 95% RO recovery design ratio (20X concentration of feed water silica levels), the HERO process can easily treat feed waters containing up to 100-ppm of silica. At a 90% RO recovery design ratio (10X concentration of feed water silica levels), the HERO process can treat feed water containing up to 200-ppm of silica. No silica dispersants are required.

Reduced sensitivity to Oil and Grease

The high pH environment both emulsifies and saponifies (forms soap) free oil and grease (typically 2 to 3 ppm) so it will not stick to nor foul the RO membrane