Reverse Osmosis and Deionized Water Filtration

Let's face it if you are in a business needing de-ionized water or reverse osmosis water you are always concerned about the quality of your water. I know as a mobile detailing business that when we have ultra clean water in our tanks we are a happy camper. We know it will make your job so much easier. We also like the idea and concept of spot free water. Have you ever considered how Reverse Osmosis really works? Let me describe the process from my industries perspective.

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In R.O. water pressure forces water through a fine membrane that filters out between 85-95% of the dissolved solids in the water. Water lacking these solids won't water spot a car. It's important to have soft water filter inline the R.O. system prior to R.O. Some systems have a water softener/carbon filter/R.O. system in that order. This saves life on the R.O. membranes. R.O. units are measured in gallons per day (GPD) because there flow is relatively slow. Usually they run twenty-four hours a day and the water is put into a storage tank to be used later. Small R.O. units that cost between ,500 and ,000 put out 4 gpm. To go to 10 gpm, the speed at which you'd want to fill your tank, the cost of those units starts at ,000.

OSMOSIS

Car washes need units that make between 500 to 1000 gallons a day for the rinse cyles. A small unit will work because 4 GPM (gallons per minute) X 60 minutes is 240 gallons. So, in four hours at night when the car wash isn't being used, they will have one thousand plus gallons. The only problem for them is that a thousand gallon tank is five feet wide and eight feet tall.

An R.O. machine works best when it's running clean water through it. Otherwise, the membranes let nature take over. Then you have not reverse osmosis but osmosis. It's better to have a small machine running twenty-four hours a day than a big machine running two hours and then shutting off. R.O. membranes should have a constant positive flow through them. Some industry leaders believe twelve to thirteen hours is the maximum you should run an R.O. unit a day. They think the machine will last longer.

Silica, iron, aluminum and bacteria cause irreversible damage to membranes and that's why pre-filters are a must to keep membranes from fouling. Fouling results when particles suspended in the feed water are deposited within the R.O. unit. Fouling reduces permeate flow rate. Bacteria fouling usually doesn't cause the permeate conductivity to increase until your system is extremely plugged. Other particles may cause permeate conductivity to increase.

Most biological and particulate silica foulants can be removed with the proper chemicals. Bio-fouling is a problem. Pre-treatment may have little impact on R.O. unit fouling. Simply killing the bacteria won't work because the same number of fouling particles (living or dead) still enter the R.O. unit. The best way to handle bio-fouling is cleaning the equipment and the upstream pipes and filters. Chlorinated water will be bad and should be un-chlorinated before entering the R.O. unit. Fouling by non-living particles is handled by your pre-filters, or additional sediment filters or cartridge filters with a nominal filtration rating of five microns or less. This can be complicated stuff and you can call your franchsior for a telephone number of a fair and honest local or regional water purification consultant.

Chlorine is the most common agent to chemically attack and destroy the polyamide thin film membranes that are commonly used in car washes. Activated carbon blocks are used generally in filters upstream from R.O. units. Larger units use granulated carbon filters or other methods. Active chlorine consuming sites on the activated carbon material is depleted over time and eventually dechlorination will diminish and finally cease. This will allow chlorine to damage downstream chlorine sensitive membranes in your R.O. unit. Carbon filters must be replaced as frequently as their manufacturers specify.

Most commercial R.O. units are too small to justify installing instrumentation to determine when to clean them. Cleaning periodically can remove most scalants and foulants. If you wait too long permanent damage will be done and proper cures will not work. If you wait until you have low flow problems, the elements may be plugged significantly and chemical cleaning may be ineffective or may take many hours to get the elements back to near original performance.

If you want, you can have the R.O. dealer do periodic cleaning on a service contract. It may be worth your while. Expect to pay between to 0 per quarter. Watch for parts price gouging. Some companies are like sharks. If well taken care of, the membranes will last years. You may want to have a technician also check upstream filters. That way, if anything does go wrong, it's their responsibility and you can make them pay. Make sure your contract is tied to their lifetime warrantee. Regular Maintenance Of Reverse Osmosis Units is ultra important and you should change your prefilters often. Water softeners every month, carbon filters quarterly. Be sure to check the pressures weekly and membranes will need changing every so often too. Think on this.

Reverse Osmosis and Deionized Water Filtration

OSMOSIS

The Different Purification Processes Involved in Deionized Water

Long ago there was little concern to thoroughly purify water because pure water had extremely few applications. In the modern times, however, there is an increasing demand of water in its purest possible form. Water is never absolutely pure. It always contains impurities such as minerals and bacteria in varying amounts. Water being a general solvent allows dissolution of many substances which contribute to its impurity.

The presence of water impurities has become a problem since the dawn of man on this planet. Diseases like cholera have been blamed to contaminated drinking water and until now it remains a problem. But centuries ago when water purification was not as sophisticated as today's, these problems were fatal. Water is a favorable environment for microorganisms like bacteria. Aside from microscopic organisms, other impurities may be present. Water always comes with dissolved minerals like calcium and magnesium. These minerals may be beneficial at times. At other times, they are just not needed. Water that contains high amounts of these minerals is called hard water. Hard water forms scum with soap. This scum adheres to sinks and tiles forming yellowish deposits. The same thing happens to clothes, which sustain yellowish discoloration upon washing in hard water.

INVERSE OSMOSIS

Purification of water is essential in many industries. Manufacturers prefer water at its best purified form. There are lots ways to remove water impurities and one is through de-ionization.

As mentioned earlier, calcium, magnesium, sodium and chloride are some of the ions present in water. The removal of these ions requires a process called ion exchange. The positive and negative ions (cations and anions respectively) present in the water are exchanged with hydrogen (H+) and hydroxyl ions (OH-). Notice that H+ and OH- are actually ions of water itself - H2O. This mechanism involves the use of resin, which has an affinity for ions. The resin beads used for this purpose contain binding sites for ion exchange to occur. After a time, the resin beads become depleted of their ion exchange capacity and they lose ion affinity. When this happens, a concentrated acid and an alkali are introduced into the resin bed. This removes accumulated ions through a process called displacement and at the same time restores H+ and OH- ions in place.

The effectiveness of this process is determined by the resulting water quality itself. Such outcome depends on a few factors. The kind of resins employed affects the process. Some resins are used for softening. Others are for demineralization. The capacity of resin to undergo regeneration is also another factor.

There are a few ways to test the quality of deionized water. This type of water contains much lower amounts of ions as the name suggests. Thus a good way of testing is through the resistivity and conductivity of water that results upon analysis. Water that is pure is never a conductor of electricity. It is the presence of ion impurities that water becomes a conductor. Thus water with extremely low amounts of ions, almost negligible, has an extremely low electrical conductivity. To make this more apparent, the amount of dissolved ions in water determines its conductivity and hence resistivity. Note that resistivity is the inverse, the opposite property of conductivity. The two properties are generally used to determine ion concentration and assess water quality.

A major problem in this process has something to do with temperature. Physics has it that temperature affects water conductivity. Thus the temperature for measuring water conductivity is standardized internationally at 25 degrees Celsius. This allows validity and reliability of data anywhere in the world. Another concern springs from the precision of temperature measurement. Ordinary water has a conductivity that changes by 2% in every degree Celsius rise in temperature. This change in conductivity, however, changes dramatically as the amount of ions decrease. Hence, deionized water samples can have conductivities that change by as much as 10% per °C change. This means that precise temperature is vital.

The Different Purification Processes Involved in Deionized Water

INVERSE OSMOSIS