Commercial Reverse Osmosis Systems

Technical Information On Reverse Osmosis Water Purification System

We rely on a variety of computer programs to design systems tailored to your specific water supply and application needs.

Our system will meet or exceed. customer expectations!

Commercial Reverse Osmosis Systems and Water Purification

(RO) membranes are the most common and popular in use. Most are polymer-based and will remove 98% of all dissolved solids (salts) present in the feed stream in a single pass. This removal percentage is called Rejection. By taking the product water from one or a number of membranes called the first pass and putting that water through another membrane or group of membranes we create a two-pass system, which can remove well over 99% of the dissolved solids resulting in deionizer/distilled quality water. Product water is called Permeate.

The dissolved solids in water are measured as Total Dissolved Solids (TDS). The TDS meter simply passes a small electrical current between 2 probes and measures how conductive the water is or conversely the resistance of the water. The reading is expressed as Parts Per Million (PPM) of dissolved solids which is essentially the same as milligrams per liter (mg/l). This translates to how much “stuff” is dissolved in the water – the higher the number the more dissolved solids.

NOTE: at this point, you can see that debris in the water -i.e. things you can see — do NOT contribute to the TDS as they do not conduct electricity. Normal system efficiency is 50% — 2 gallons in, 1 gallon treated and 1 gallon to drain.

This is called Recovery. With proper pre-treatment, membrane selection, and flow pattern design, the recovery can be 85% or higher. As recovery increases, however, rejection decreases so there is a sacrifice in water quality. As a general rule, it takes 1 PSI across the membrane for every 100 parts per million to get the first drop of water to pass through. To achieve a reasonable flow most systems operate in the 125 to 250 PSI range depending on the raw water quality and membrane selection. Fresh water membranes are used to treat water up to about 10,000 PPM.

The rejection process is electrochemical in nature so the small holes (porosity) of the elements are there for water passage not to reject dissolved solids. This porosity is in the range of 0.001 microns making it an excellent “trap” or filter for bacteria and viruses but makes the elements susceptible to plugging by oxidized materials such as iron. The most critical aspects of a membrane system design are knowledge of the raw water chemistry, customer water needs, membrane selection, membrane array (flow path), pump curve selection and pre-treatment.

Though stated last, pre-treatment is vital. Control of suspended solids, colloids, silt and bacteria must be done because of the 0.001 membrane pore size. Calcium hardness must be addressed to avoid membrane scaling. Seldom if ever are softeners employed for the scale control as they have been generally replaced with physical water treatment to suspend the hardness or chemical feed systems feeding a mild acid and surfactant compound called an anti-scale chemical. Iron and manganese control also is imperative and is often treated with simple filtration or the anti-scale chemical. Most membranes are free chlorine intolerant so it too must be eliminated either by activated carbon or with a chemical feed of a sodium sulfide compound.

Lastly, feed water temperature must be viewed. Water like oil becomes more viscous as the temperature decreases so pumps and pressure vessels need to change for low temperatures to maintain production levels. Above 110 Deg. F. membranes deteriorate so intermediate cooling may be necessary.

Seawater Membranes

Virtually everything stated above about standard RO membranes applies to the seawater equipment. Because the TDS level of seawater is 32,000 to 45,000 PPM the driving pressure must increase. Using the general rule of 1 PSI per 100 PPM, the first drop of water is passed at 320 PSI.

To achieve meaningful flows, the seawater systems operate at 750 to 1200 PSI. This obviously requires stronger internal support of the membrane itself, higher pressure membrane vessels, more robust high-pressure pumps, high-pressure piping and materials throughout that can tolerate the corrosive effects of seawater. If there is an abundant source of seawater for supply, systems are designed for recovery in the range of 25% to provide the best quality of treated (permeate) water in the range of 150 PPM.

Normally, higher recovery levels of 60% are designed and the systems maintain a permeate level less than 500 ppm, which is a World Health Organization (WHO) standard. As systems get larger, it is common to route the drain water to a device attached to the high-pressure pump motor to recover energy thus reducing electrical costs. Suffice to say, with all of the complexities and high pressures, this type of equipment does not lend itself to novice manufacturers.

Nano Membranes

These are hybrid membranes that are specifically designed to remove certain dissolved solids in the raw water while leaving others. All dissolved solids exist in an ion state. Each ion has a specific number of electrons in its outer shell. The number is referred to as the valence. One being monovalent, two being divalent, etc. The higher the number the greater the attraction to the membrane and thus the higher the removal rate –rejection.

Where standard and seawater membranes are formulated to low as well as high valence numbers, NANO membranes are formulated to selectively reject divalent and higher with an only mild rejection of monovalent ions.

The most prevalent divalent ions are Calcium, Magnesium, Carbonate and Sulfate. These are all associated with hardness so NANO membranes are often thought of and used as membrane softeners. The total rejection level of the membrane is a function of the monovalent concentration but experience indicates a level of 80% recovery. The NANO membranes operate at about 80-100 PSI so the systems use less power. Pore size is in the 0.01 micron range so bacteria and viruses are essentially blocked. The same cares and concerns relative to pre-treatment and component selection that is expressed for standard RO systems apply.

Ultrafiltration (UF) Membranes

Unlike the above-listed membranes, the UF membranes are not designed to reduce dissolved solids. They are strictly a filter as the name implies. They are selectively available with pore sizes from 0.01 to 0.20 micron. Recovery rates are in the 90% range and they operate on pressures ranging from 2 to 50 PSI. In water treatment, they are employed for colloid, silt, tannin, and bacteria removal often as pre-treatment for reverse osmosis systems. In the processing and waste industries, the applications are limitless – whey recovery for cheese plants, dye removal, dairy solids concentration, yeast separation, tertiary wastewater purification, etc.

Membranes are available in hollow fiber style (bundles of hair-like hollow tubes with inside out or outside inflow). Though on the surface the UF process appears simple, in practice it is actually more complicated than reverse osmosis or NANO because of the chemistry and hydraulic knowledge needed to produce exactly what the customer requires. We invite any and all questions.

To enhance your understanding of membranes and their applications in commercial reverse osmosis systems, pre-treatment and expected results we suggest the book “Reverse Osmosis” by Wes Byrneor the Hydranautics web site www.membranes.com.

Cartridge Filters

Cartridge filters are sediment filters used to reduce the amount of sediments transported by fluid through filtration. They are preferable for systems with contaminations lower than 100 ppm.

Chemicals

The chemical treatment of water employs using an extensive palette of chemicals, according to your water issue. From algaecides, biocides, corrosion inhibitors, to disinfectants, flocculants and scale inhibitors, Dime Water Inc. provides everything you need in term of chemical water treatment.

Membranes

Commercial reverse osmosis systems membranes are the most common and popular in use for removing dissolved solids present in the feed stream. Membranes used for RO have a dense layer in the polymer matrix where the separation occurs.

Control System Components

Control system components cover all types of water treatment system control products, counters, timers and various control devices. We have all components we use in stock or if not we can procure anything that we utilize in our controls systems within 24 hours.

Faucets

Faucets are basically valves used to control the release of a liquid or gas. We can provide our customers with various faucet designs.

Diaphragm Control Valves

Used in a variety of contexts, control valves regulate the water flow based on signals received from system controllers by fully or partially opening or closing, which is done automatically by actuators.

Call Dime Water at 760.734.5787 to purchase any of these parts.

A water treatment system or commercial reverse osmosis systems service and maintenance plan is an economical interference-free manner in order to ensure that the water treatment system is operating at the desired performance. Our approach is – on a local basis including much of southern California – to use contractors’ help. More often than not, we are able to provide a plumber or a licensed technician that will work on our behalf to get the equipment repaired. We are available from 8am-5pm, Monday to Friday to answer all your questions!

Dime Water, Inc. provides pre- and post treatment instructions with every system at the time of the shipment. Our staffed engineers will be in touch with you to answer all your questions about pre- or post treatment. If you have any questions, call and talk to our water treatment experts.

Common Issues with Reverse Osmosis (RO) Units

• The number one problem is that people throttle the drain or turn the drain down too far and that prematurely destroys the plugs, the membrane. Another issue we often run into is that clients have either inadequate or no pre-treatment and a typical RO unit is going to fail prematurely. The third thing is the control system; there are digital, electronic and electro-mechanical control systems and if the controls aren’t working very few suppliers will provide adequate wiring diagrams and information. We at Dime Water, Inc. give out all the information possible to keep the control systems working or to be able to diagnose a problem of the control system. Another problem that we run into has to do oddly enough with the weather; when the water gets cold the production starts to go way down and people are not aware of it so it’s kind of a false problem – usually around October they start calling that their water production is going down; in these situations there is nothing wrong with the unit it is just that the water is getting cold.
• No water or poor water flow from the pump system: the high pressure pump could have a poor power going through it, we often run into that the voltage in the house or the voltage in the building has dropped because it’s like in hot weather everybody’s got their air-conditioner on and the voltage goes down and the pumping capability goes down. It could also be a tear in the pump, it’s old and has to be replaced.
• Feed water valve is plugged or closed: the type that we use has a bypass in the valve so that you could turn a little lever or turn a little dial and force it to open that way; otherwise all you can do is replace it.
• Pre filter or carbon post filter is clogged: you have no choice but to replace it.
• Water pressure: typically 20-25 psi while the unit is running.
• Commercial reverse osmosis systems membrane is broken: there is no repair, if it is dirty it can be sometimes cleaned but if it is not producing at all or producing high TDS water it should be replaced.
• Air pressure in holding tank is not correct: if the air pressure is too high the RO unit gets a back pressure and the result is poor quantity of water produced by the RO unit; if the water pressure is too low in the tank, then toward the end of emptying the tank you’re going to get dissatisfied with the volume of the water coming out of the faucet.
• Airbladder in holding tank is ruptured: the air will eventually saturate and dissolve into the water and it is just a matter of time and the tank will be totally full of water and no pressure to force it out, so you won’t have water coming out at all; you need to replace the tank, or some bladder tanks have replaceable bladder in them.
• No water to drain, drain flow restrictor in clogged: this needs to be fixed in a hurry because when you don’t have enough water going to drain, very soon you are going to destroy the membrane.
• No water to drain, air gap faucet is clogged: you will get a buildup of airborne bacteria that just grows and grows in the lines and eventually plugs it and there is no water to drain.
• Check valve on commercial reverse osmosis systems membrane housing is stuck: if it is stuck in the closed position all you can do is replace it; if it’s stuck in the open position you got to be very careful because in a short period of time, we are talking hours, it’s going to destroy the membrane.
• The automatic shut off valve is malfunctioning: there is a single little diaphragm in there and if the diaphragm is ruptured you are going to have to replace the valve, there is really no way to repair them.
• Low water pressure from the dispensing faucet: if it is toward the end of the tank, in other words you get a few glasses of water and then the water slows down it just means that you have a very low pressure in the tank and you need to increase it; typically you should have in the neighborhood of 10-15 psi in the bladder tank when it is totally empty.
• Water TDS in the RO system is high: one reason is that you might have low pressure in the unit, the other problem could be that the water is warmer than normal and the TDS goes up; another reason could be that the product water tube is not fully engaged with the housing, so you are getting some mixing of raw water with product water, and the last thing would be that the membrane itself is now defective.
• Taste and odor in the product water from RO: this means that somewhere you have a growth taking place in the tank and what you should do is either try to sanitize the tank, which is quite difficult or just replace it. It is probably more economical to replace it than it is to try to sanitize it.
• Drain water overflows at air gap faucet: it is the buildup of the airborne bacteria and microorganisms in the air; you have to take a pipe cleaner and try to unplug it or try to kill the bacteria with bleach or hydrogen peroxide;
• Faucet drops or leaks: typically it is just a little spring loaded valve what most manufacturers sell and you don’t have to replace the faucet, what you do is turn the water off at the tank and at the inlet to the RO unit and then pull out the dispenser spout and then if you look you’ll see that there is a way to unscrew the valve and put in a new valve repair kit.
• Dime Water, Inc. provides pre- and post treatment instructions with every system at the time of the shipment. Our staffed engineers will be in touch with you to answer all your questions about pre- or post treatment. If you have any questions, call and talk to our water treatment experts.
• What can you check if the water softener is not working?
• Look for the bypass valve, almost all water softeners are installed with a bypass valve; the bypass valve might be open and that is why there is no soft water.
  Look to see if there is adequate amount of salt in the brine tank; the salt level always has to be above the water level, if not, you are not getting saturated brine you just regenerating with water and you are going to have hard water.
• Check the valve itself – the water softener is plugged in an outlet that’s on a switch, so when you turn the light off you turn off the water softener and there is no electricity to it and therefore the unit will not regenerate the way that it should.
  Especially if you are on city water the chlorine in the city water will eventually wear out the water softener resin so keep that in mind because it will shorten the life of the water softener.
  Water hardness can change so if your unit is set up for one hardness value and over a period of time the water hardness got greater, the water softener does not know that and you are going to end up with frequent hard water coming out of the unit.
• Check the controls, these might be set up improperly.
• Check the drain line – if you moved something around in your home or garage or basement you could have pinched or obstructed the drain line and once that is obstructed the unit will not regenerate properly, it will consume salt.
• Common Issues with Water Softeners
• System is not sucking water from brine tank
• There is an injector that creates the suction; in the injector because of dirt in the water or iron in the water will often become plugged; the injector has to be cleaned.
  Over a period of time the tube going from the control valve to the brine tank can age and get a crack in it and instead of drawing in brine just draws in air
  If for whatever reason your water pressure is gone way down then you are not going to draw in brine
  Look for the obstruction of the drain line
  Error code on the digital meter
• Check the manual of instructions and see what different error codes mean, then correct the problem (there are about 2-10 codes that can appear approximately – there are no standard codes you need the manufacturer’s own manual)
• Getting resin in the house after installing the water softener
• This means either that the unit was installed backwards with the inlet and outlet reversed and that will cause the resin to go out (we put upper screens on our units to prevent this) or the lowest distributor got broken out of carelessness, also if the unit froze in transit that could cause the problem as well.
• Possible of elevating the drain line above the water softener
• It takes 21/2 feet of elevation to act as a 1 pound backpressure so if you got reasonable pressure in your home, meaning somewhere between 30-40 psi, the elevation of a drain for 8-10 feet is not going to make any difference at all.