US 9,073,763 B2  26  25  TABLE 5-continued  TABLE6  TABLE 7  Notes:  1. Analysis of RO feed is not shown in the table, nor is the hydroxide content ofRO reject and  RO Product.  2. The chemistry is based on 90 percent RO recovery, while maximum recovery feasible is  approximately 96 percent.  3. Except for pH, all constituents are reported as mg/1 as CaCO$_{3 }$ Compared to 60 to 70 percent boron rejection in conven› tional thin film composite RO operation, the new process  provides approximately 99 percent boron rejection. In a  double pass configuration, the new process is capable of  producing a permeate with lower than detectable limits of  boron content.  Note:  See Section 5.0 for basis.  Another very significant advantage in operating ion  exchange with permeate from a HERO brand RO system is  that sodium leakage from cation resin is reduced by several  orders of magnitude, due to the high ambient pH of the  influent. As a result, longer run times between regeneration  for existing ion exchange systems means lower chemical and  manpower needs, lower regeneration waste volume, etc. For  new systems, or for existing systems undergoing expansion,  the new HERO brand RO process design and operation can  have a strong positive impact on the ion exchange system  capital cost as well.  (B) High Recovery Rates  Since hardness-causing ions such as calcium, magnesium,  barium, strontium, aluminum, iron, manganese, etc., have  been removed prior to the RO, undesirable precipitation of  species such as calcium carbonate, calcium fluoride, calcium  sulfate, barium sulfate, magnesium hydroxide, aluminum/  magnesium silicate, etc., does not occur in the HERO brand  RO process, and thus that type of precipitation no longer  limits the recovery achievable by an RO system. Importantly,  silica solubility, is increased dramatically at the normal  HERO brand RO operating pH (preferably of approximately  11 ). Sustainable long-term operation with silica levels in the  450 to 500 ppm range (in the RO reject) has been proven, and  It  has been known ( and practiced) for almost 30 years that  softening of RO feedwater destabilizes colloidal solids  present in the feedwater and significantly reduces the associ› ated fouling problems. Mandatory softening requirement as  pretreatment for hollow fine fiber RO elements in the late  1960s and early 1970s attests to this strategy. In addition, zeta  potential is generally reduced between a surface and foulant  particles at high pH, thus reducing the likelihood of adhesion.  This property is accentuated by the fact that most naturally  occurring particles (including bacteria) exhibit negative sur- face charges. While side-by-side zeta potential determination  is yet to be carried out, the new process is expected to signifi› cantly reduce, if not eliminate, particulate fouling problems.  (D) Particulate Fouling is Substantially Reduced  (C) Biological Fouling is Essentially Eliminated  theoretical models indicate that levels of 1,000 ppm or higher  may be achievable in this new RO operational method.  Based on 25 ppm silica in the RO feed, 95 percent recovery  RO operation (approximately 500 ppm in the reject) has been  proven by testing. Still, 97 .5 percent recovery ( approximately  1,000 ppm silica in the RO reject) is theoretically feasible,  whether or not practical from an operational point of view.  Since silica usually represents the ultimate limiting criterion,  in terms of maximum allowable recovery in an RO system,  increased silica solubility along with essentially total absence  of species such as calcium, barium, etc., in RO feed, should  allow RO operation at very high recovery rates (90 to 98  percent) with the vast majority offeedwaters.  With feedwater relatively high in barium content, RO sys- tern recovery can be limited by barium sulfate precipitation  potential at the reject end. The HERO system eliminates this  concern altogether, since barium is quantitatively removed  prior to the RO. The same outcome is also applicable for RO  systems limited (in recovery) by strontium sulfate, calcium  sulfate, calcium fluoride, and other sparingly soluble cal› cium, magnesium, iron, and aluminum salts.  Of course, the final limit in RO recovery, represented by  osmotic pressure of the RO reject, will still control the maxi› mum feasible recovery achievable with a specific feedwater,  but this limit is not usually reached at recoveries less than 99  percent with most feedwaters.  Most commonly occurring microbial species are com› pletely lysed (physically destroyed) at the high operating pH.  In fact, even virus, spores, and endotoxins are either  destroyed or rendered incapable of reproduction/prolifera› tion at very high pH levels. Saponification of lipids (fat) is  expected to play a role in the process as well since fatty acids  and their corresponding glycerides will form soluble "soaps"  at the high operating pH.  In one location where long-term tests were carried out,  biofouling was conspicuous by its absence during the test of  the HERO technology. This pilot RO system exhibited very  stable operating performance in terms of normalized perme- ate flow and system pressure drop throughout the test period.  Further confirmation of the absence of biofouling was  obtained during autopsy of RO elements at regular intervals.  A stage wise program to test and autopsy the FILMTEC FT30  based elements was conducted over a 15 month period. The  data showed higher salt rejection than the initial Quality  Assurance values under standard test conditions. Also, the  membrane surface was clean and free of any evidence of  biofouling.  This characteristic of the new process can be of significant  benefit for sites with known biofouling problems or for the  treatment of bio-contaminated/bio-active wastewater.  It  can  also be very effective for systems with higher-than-ambient  temperature RO operation.  SiO2  pH  WATER ANALYSIS  Raw Water  50  7.1  RO Reject  500  10.8  RO Product  <1  10.2  COST ESTIMATE OF A RETROFIT  Water/Waste Water Savings  Antiscalant Elimination  Power Savings  Additional Chemical Costs  Additional Miscellaneous Costs  Net Annual Savings  Conversion (Capital) Cost  Simple Pay-Back Period  244,000 US $/Yr)  30,000 US $/Yr)  17,000 US $/Yr)  (40,000) US $/Yr)  --~(2_0_,o_o~o) us $/Yr)  231,000 US $/Yr)  200,000 (One Time)  10.4 (Months)  COST COMPARISON  Conventional  HERO  System  System  Equipment Capital Cost (US $MM)  Operating Cost (US $/1.000 US Gallon)  12  5.75  7.8  <4.00 