Whats so different about the MaxCap RO/DI System??

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What makes the MaxCap™ RO/DI System so special?

An RO/DI system is a set of discreet technologies that must be properly integrated to optimize pure water production and minimize operation costs. In general, a water system is only as good as its weakest component. We wrote this little guide to highlight the challenge and describe the benefits of integrating the best-of-the-best components into the new MaxCap RODI systems.

Basic System Design Considerations
In a properly designed RO/DI system, the most vulnerable and expensive components are placed nearest the point-of-use and are protected by upstream water treatment components that are less vulnerable and expensive. For example, the DI cartridge is the last component in the chain of purification and is one of the most vulnerable and expensive. It is protected by the preceding reverse osmosis membrane that, in turn is protected by the carbon block filter that is preceded by the sediment filter. If any one of these critical components is not properly selected or is of sub-standard quality, premature failure of downstream components can result. This is expensive and can cause grave consequences to the stable conditions of the reef tank environment.

Water Quality
Water quality is commonly measured in units of total dissolved solids (TDS) and is desired by most to at least be less than 1PPM indicated on a reliable sensitive instrument. Be careful of systems touting “ZERO” TDS. Such systems may have Zero Indicated TDS, which may or may not be ultra pure water depending on the sensitivity of the instrument used to measure the purity of the water. Ultra pure water is about 18.2 Mohms or about 0.05 micro siemens. Thus, if there were such a thing as "ZERO TDS", it might be more appropriately measured around 0.05 micro siemens. Unfortunately, most inexpensive TDS meters can resolve at best about 5 micro siemens. That is several decades lower sensitivity than required to be stating so called "ZERO TDS" or “Ultra pure water”. While 5 micro siemens conductivity is very reasonable for break-through detection to signal cartridge replacement required, it is clearly not sufficient to measure or claim “ZERO TDS”. For a better measurement tool, we recommend a COM-100 handheld meter, or other suitable instrument having similar or better sensitivity. All MaxCap™ systems are designed to reliably produce ultra pure, 17-18 Mohm water.


Sediment Filters
First, let's talk about sediment pre-filters and the difference between absolute and nominal micron ratings. In an absolute rated filter all particles larger than the stated micron rating are removed by the filter. In a nominal rated filter a certain percentage of particles larger than the nominal rating will actually pass through the filter. The % efficiency rating of the nominal rated filter tells you how many of the larger particles will pass through. Most sediment filters are of the nominal rating variety. String wound and spun filters have a low % efficiency rating and offer little protection for downstream components. Resin bonded sediment filters offer a very high nominal % efficiency rating and offer good protection. Some micro-sediment filters are absolute filters and provide superior protection of downstream carbon filters and membranes.
The MaxCap™ uses our new ZetaZorb™ sediment filter which has truly amazing filter capacity (about five times that of any other sub-micron sediment filter), resulting in extremely long life in the most challenging sediment conditions. As it is a true 0.2 micron absolute filter, it has the ability to remove bacteria and viruses that can cause biofouling. Another benefit from the 0.2 micron absolute filter is your downstream carbon block filter will last much longer (2x) as it will no longer be acting as a secondary sediment filter. Instead, the carbon block can do its job of removing Chloramines, VOC's, etc. Of course, if your sediment filter protects your carbon filter, it will also be protecting your expensive RO membrane as well. Basically, your sediment filter is the first link in your total system performance, and can greatly affect your long term operational cost to produce good clean water.


Carbon Block Filters
Next in line are carbon block filters. The primary function of these filters is to remove chlorine and secondarily further filter out any remaining sediment. They are typically available in three ratings: 10 micron (removes chlorine for up to 3000 gallons), 5 micron (6000 gallons) and 0.5 micron (20000 gallons) which is also effective in removing organic chemicals such as pesticides, herbicides and trihalomethanes. Since carbon block filters are absolute filters and are prone to plugging with sediment, it is essential that they are preceded by a very high efficiency sediment filter such as the ZetaZorb™; otherwise sediment will displace available carbon sites that would otherwise be used for various organic removal. The best means of determining when to replace the filter is to test the waste water stream for presence of chlorine. Any chlorine level above 0.1 ppm will cause damage to the RO membrane and indicates that the carbon block filter must be changed. All MaxCap™ systems only use our best 0.5 micron carbon block filter for the greatest removal capacity. Protected by the ZetaZorb™, it will last its full lifespan, as it will not be plugged prematurely with sediment fines that would pass through larger pore size filters.

Reverse Osmosis Membranes
The RO membrane is the workhorse of the water purification system. It uses a thin film membrane technology to reject impurities. RO membranes are especially good at rejecting large atoms and molecules and those species that exhibit relatively strong electron charge. It is less effective in rejecting small atoms and molecules (smaller than water) and those with relatively weak electron charge. RO membranes will allow all dissolved gases (such as ammonia and carbon dioxide) to pass through. The % rejection rating for a membrane is an indication of how much of these impurities will pass through the membrane and on to the DI cartridge. A membrane that has a 98% rejection rating will pass only half as many of these impurities as one with a rating of 96%. The direct result of using a 98% rejection membrane as opposed to a 96% membrane is that you will double your DI cartridge lifetime. It is important to note that all membrane manufacturers adhere to a lower % rejection limit for small membranes (2" x 10") of 96% at 60 psi and that the only way to ensure that you are using a higher % rejection membrane is to purchase it from a source which screens for higher % rejection membranes. We have been testing our RO membranes for over 20 years to the industry standard of 60psi. There is a significant amount of data for us to draw upon
when we share performance characteristics with our customers, help them troubleshoot production problems, or back up our ratings claims, for that matter.

For example, the Filmtec 75 GPD membrane that is so popular is rated 75 GPD at 50psi. When we test it at the industry standard of 60 psi, the rating is at 90 GPD. The production rate of RO membranes is directly proportional to the applied pressure, thus the rating difference; this is why we sell our membranes and systems as 90 GPD (at 60 psi and 77F). Unfortunately, most customers in the USA have less than 60 psi (or even 50 psi) available, let alone the 77F water temp that is used in the rating process (average water temp is more like 50F across most parts of the
country). In these cases a pressure-boosting pump can obtain higher production rates. If you live in Hades (Phoenix in the summer) the 77F is not much of a limiting factor as far as production goes. But for our
customers in upstate New York in January, it is a huge factor. Perhaps to be more realistic we should all rate membranes production on systems at 40 psi and 50F, although I doubt our competitors would drop their rating convention in this highly competitive market seemingly driven by perceived cost per gallon production rate. That said, with the membranes that we hand-select and test to insure rejection greater than 98%, we typically see production rates exceeding 100 GPD at 60 psi (and 77 F)!! If you look back at their literature, Filmtec started the 50 psi rating as a sales gimmick wherein they stated that FILMTEC membranes have the same production at 50 psi as the competitors membranes do at 60psi. Great way to snag customers, but it requires customers to look at the production rate charts and how they are derived to really compare membrane production rates. With our hand-selected and tested Filmtec 75GPD membranes, we can make sure that you are purchasing greater than 98% rejection (look at their spec on the DOW website, 96% is the bottom range of the guarantee. They are not all 98% like many think). http://www.dow.com/liquidseps/prod/tw30_181275.htm

The MaxCap™ uses tested membranes to insure that rejection is better than 98%, and that production rates are at least greater than stated. The new MaxCap™ 150 and 300 use new proprietary high efficiency membranes that allow a single membrane system to produce an amazing 150 GPD at 60psi (77F). Dual 150’s produce an even more amazing 300 GPD. Our competitors can only produce 180 GPD with the same footprint (two 90GPD membranes). These exceptionally high production rates allow these systems to produce larger amounts of water than competitor systems at colder temperatures, where lower rated membranes really struggle to produce. For example, a 90 GPD production membrane output will be cut approximately in half, or 45 GPD if the water temperature drops from 77F to 55F.

Why all this worry over Rejection Rates?
Why is 1 or 2% improvement in rejection rate so important?? A 2% increase in rejection from 96% to 98% can double your DI cartridge(s) life. Over the life of the membrane that can save you big $$$ in DI cartridges! That is why our hand selection and proprietary testing (we reject more than half that do not meet our SPEC of >98.0% rejection) is worth the extra cost. Who else labels their membranes with actual percent rejection and production rates on the so called "the same" membrane?



De-ionization Cartridges
The DI cartridge serves as a final polish of the water before it sees the actual application. The cartridge contains a mixed bed of anion and cation resins that uses an ion exchange mechanism to remove the small amount of impurities that pass through the RO membrane such as silica, phosphates, nitrates, ammonium and other trace impurities. Like a filter, the DI cartridge must be monitored for performance and replaced when it becomes exhausted. The best way to accomplish this is through use of a resistivity monitor. Another way is through the use of color change resins that give a visual indication of when the resins are exhausted. It is difficult to determine the exact replacement point of color change cartridges. Failure to do so often results in dumping of silica and other contaminants back into the water. Each MaxCap™ RO/DI System uses the revolutionary MaxCap™ DI cartridge as a first super high capacity roughing cartridge. The MaxCap DI™ cartridge has 3.5 times more capacity than any other Mixed-Bed or Hi-Silica-removal deionizing cartridge. When installed upstream of a Silica Buster or other DI cartridge, the life of your downstream DI cartridge will increase significantly. This incredible breakthrough in DI cartridge technology reduces your costs to produce DI water by over 50%, often paying for the system in less than two years on savings alone in replacement DI cartridges. In most applications, the MaxCap DI™ is installed up-stream of a Mixed-Bed or Hi-Silica removal cartridge. For example, if the RO water entering the MaxCap DI™ has 20 ppm TDS (Total Dissolved Solids), the original DI cartridge may process about 400 gallons of pure DI water. By placing a MaxCap DI™ cartridge in front of the original cartridge, 1200 gallons of water will pass through both cartridges before the MaxCap DI™ is exhausted. The original DI cartridge will be only one-third exhausted. A second MaxCap DI™ will process another 1200 gallons and the original cartridge will now be two-thirds exhausted. Only after a third MaxCap DI™ cartridge processes another 1200 gallons will the original cartridge finally become fully exhausted. That's 3600 gallons purified with only 4 (3 MaxCap DI™ + 1 Mixed-Bed) cartridges, not 9 (9 x 400 = 3600). The MaxCap™ systems use the Silica Buster™ as the second stage of DI polish to insure that silica removal is at its highest, and to make sure the product water is ultra pure.

Cost of Ownership
There are at least two costs when purchasing a RO/DI system, the first everyone is aware of is the initial purchase price, and the second is rarely given much thought; the cost to operate and maintain the system to produce water. This second cost is often overlooked during the excitement of the initial purchase, which is unfortunate as often the cost to maintain and operate the system chosen exceeds the system purchase price within the first year or so. For example, poor sediment filtration will result in premature carbon block filter life, which in turn prematurely consumes the RO membrane by increasing its load factor. As the deteriorating membrane rejection rate allows a larger downstream load of impurities to pass to the DI stages, their lifespan is correspondingly decreased. Each system is only as good as the weakest link. Each must be carefully selected to optimize performance. Under Phoenix Metro water test conditions, the MaxCap™ RO/DI 90, 150 or 300 will typically pay for itself in less than one year over any competitor system in savings due to its total system integrated performance, top notch components, and proprietary membrane, sediment filtration and DI cartridge technology.


Charles Mitsis
Bruce Huling
SpectraPure