Erdington Aquatics UK & Aquatic-Store.co.uk

This article is taken from the Kent Marine 2002/2003 Catalogue. It is of American origin. The subject is: Water Filtration.

Reverse osmosis (RO) is a process which purifies water by forcing it through a fine membrane, which leaves impurities behind. This is probably the most practical option for the hobbyist, especially if larger amounts are required, i.e. for multiple tanks.

The water in our taps is filled with all sorts of toxic materials. Among these can be lead, mercury, arsenic, chromium, pesticides, herbicides, industrial pollutants (tetrachloride, vinyl chloride, benzine etc.), gasoline, and trihalomethanes (reactions between organic matter and chlorine), chlorine, radium, and radon gas to name just a few. These substances are toxic to humans and to aquarium fish. Some fish, such as discus, are also sensitive to hardness (sodium and calcium compounds). Phosphates and silicates cause rapid growth of undesirable algae's in both fresh and salt water aquariums. This is particularly true in “reef” type aquariums.

Distilled water is available at many supermarkets, but how pure is distilled? Many distillers may use copper with soldered Joints, similar to household piping. Copper and lead are toxic to fish. “Naturally pure” spring water is available, however, water is the “universal solvent,” which means all sorts of minerals will be present. These waters also are high cost. Usually about 50 cents to $1 .00 per gallon. The real solution is water made at home. There are two ways to go, deionization or RO. (Osmosis) or a combination of both. No single answer exists for every water system, however, since everybody’s water is different. Some municipal water systems contain high levels of chemicals which can cause problems with any filtration system - see the paragraph on potential problems below. Just remember, you must purchase a system which will meet the needs of your situation, so educate yourself as much as possible prior to purchase.

The Kent Marine DEION unit is a cation and anion exchange resin filter, with a carbon pre-filter, which will remove dissolved solids similar to an RO. unit. It wastes no water, is designed for connection directly to your household piping system, and has replaceable or regenerative cartridges. Water costs about 10 cents per gallon if resins are simply replaced, or 1 to 2 cents per gallon if they are regenerated by qualified persons. [ requires use of dangerous chemicals and must be done by qualified persons) The DEION will produce anywhere from 50 gallons to 500 gallons of water between regenerations. This is entirely dependent on what is in your water. If your water is very hard, it will produce less, if it is very soft, the DEION will produce more water between regenerations. DEION units typically will produce better quality water than RD units, but for a much shorter time, and with more maintenance.

For most people, the RO unit is the better choice, because it less expensive to operate, and requires less frequent maintenance. The RO unit utilizes a membrane, under pressure, to force water to leave its pollutants on one side of the membrane and produce water free of dissolved solids on the other. The units “waste water,” a drawback. However, Kent Marine R/O’s waste only 4 gallons of water for every 1 gallon of product water (The 50 gpd TFC unit wastes only 2.5 gallons to 1). Some manufacturer’s units waste up to 10 gallons. For most areas of the country, R0 is the only reasonable alternative. They will produce water for about .5 cents per gallon and the membranes will last for 5,000 to 10,000 gallons of product water if properly cared for!

RO daily water production ratings are nominal. A 10 gallon per day unit will produce about 10 gallons of filtered water per day when supplied with a pressure of 65 PSI, and water containing average TDS (dissolved solids). If your TDS is high (you have very hard water) or your pressure is low, your RO unit will produce less water per day. This is a fact of life. So - if you need exactly 24 gallons of water every day, and you know you have hard water or low pressure, DON’T buy a 24 gpd unit. Go to the next larger size. There are three types of membranes, CTA or Cellulose Triacetate, TFC or Thin Film Composite and Hi-S high silica removal. Which do you need? The CTA membrane is less expensive, It will remove above 90% of most pollutants, and together with an activated carbon post filter, will provide all the filtration required by people and most aquariums. Water must be chlorinated to use the CTA membrane, that is, don’t use it on well water systems unless they are chlorinated regularly.

The TFC membrane is more expensive. It must have carbon filtration ahead of the membrane, to remove the chlorine. Chlorine will ruin the membrane. This requires all water, both product and waste to flow through the carbon filter, exhausting it much quicker and requiring frequent changes (5 times as often). Forgetting to change the carbon filter will cause the membrane to fail. The TFC membrane removes a little higher percentage of most pollutants. The Hi-F, High Flow RO Membrane, provides large amounts of RO water with the removal percentages of a TFC membrane. Many other high GPO membranes lack the water quality that the Hi-F can provide. The Hi-S system, a Kent exclusive, has the highest removal ratings, on average, of any membrane type. This membrane is slightly more expensive than the TFC, but the benefits out weigh the cost difference. These membranes are able to remove 99-99.5% of the silicate from the tap water. The CTA only removes 80-90, and the TFC removes 92-95%. If brown diatom algae is a problem in your aquarium, the Hi-S system might help. The main difference between OTA, TFC, and the Hi-S membranes for aquarists is that nitrate removal for the CTA is 50-70%, TFC is 95%, and the Hi-S is 96%, so the question is do you have high nitrates in your tap water, and do they cause problems in your tank. If the answer is yes, then purchase the TFC or Hi-S membrane. If the answer is no, then purchase the CTA membrane. In about 75% of cases, the TFO or Hi-S membranes makes the most sense. So, if you just can’t decide, go with the TFC or the Hi-S. No matter which membrane you use, the water must be tested microbiologically. We do not recommend that you drink de-ionized water.

High levels of iron, manganese, phosphates, chlorine, hydrogen sulphide, or chloramine etc. can cause problems for your water treatment system. You may need to contact Kent Marine for help when these problems occur. In some cases, special pre-filtration may be required ahead of the RO or DI unit. If you live in an area with exceptionally high phosphates, say over 1 ppm, you should consider an RO unit followed by a DEION to get the phosphates low enough for a reef tank. The Maxxima combines the best attributes of RO and Deionization all in one system. If the chlorine or chloramine in your area is over 1 ppm, you should contact the factory for help in designing your water system. Or, in this case, contact Erdington Aquatics, where we have experts on hand to help you.

The above tables are part of the article on water filtration. I do not even pretend to understand much of this, if any, but I hope that it is of help to those of you who understand the scientific aspects of good old H2O!!