Water Filtration Systems: Operation and maintenance issues

Feb. 1, 2004

Operation and maintenance issues of these often overlooked accessories
By Joe Escobar

Don't drink the water. Many commercial airlines post this warning in their lavatories over the water faucet. But what about water that is meant for consumption? What kind of filtration systems are necessary to ensure a high degree of water quality is maintained? What should we keep in mind when maintaining water filtration systems? This article will look at different types of water filtration systems and some maintenance issues to keep in mind when working with each system.

Carbon filters
The basic water filter in an aircraft is a canister-type filter. There are many different types of filters. Everpure is one manufacturer of canister filters for aircraft. It has four different type cartridges: granulated carbon, carbon block, granulated carbon with polyphosphate, and a septum type filter. Jerry Letcher, sales manager for Plymouth Products, discusses the reason for offering different types of filters. "Our different filter applications are meant to meet the different requirements of the operators. Where they are flying and the type of water they are filling their tanks with affects which product they will use."

One issue pertaining to water quality is water turbidity, or water with high amounts of particulates in it. In that case, Letcher would recommend the septum filter. "Our 150GY filter is a septum filter. The septum is a fabric material that is installed in a kind of an accordion shape. A proprietary carbon mixture we call Precoat then coats the septum. As the water passes through the filtering media, chlorine and sediment are removed."

Odor and taste
In other cases, the main issue to address is odor and taste. To address that, you basically want to remove the chlorine from the water. Any one of the filters would work well with that, as carbon is responsible for removing odor and taste from water.

Preventing scale buildup

One particular filter addresses the problem of scale buildup. It is the granulated carbon with polyphosphate. Marcus McLeod, project engineer for Plymouth Products, explains how polyphosphates work. "Polyphosphates help to reduce scale buildup on heating elements and different surfaces as well as in cold applications in different types of ice machines. It helps hold the scale in the solution to keep buildup to a minimum. It also has some corrosion inhibiting factors in it as well."

Filter replacement
The process of replacing filters in canister-type filters can seem pretty straightforward. You just remove the old filter and install the new one, right? Well not quite. There are other factors to keep in mind. For one, you need to make sure you have the right filter to install. In the case of Plymouth filter products, the same canister can accommodate different filters. It can be quite easy for someone to inadvertently install an incorrect filter. Be sure to check your manual to ensure the correct filter is installed.

Letcher also stresses inspecting the gasket material while the canister is apart. "You want to examine the gasket. In our product, it's a square-cut gasket that seals the two parts together. You want to check and make sure it is OK. Check for cuts, twists, and any type of damage to the gasket."

Wash out the shell
Another thing to keep in mind is to clean out the shell of the canister when you have it open. McLeod stresses, "Our labels ask that the shell be washed with a bleach solution when you change cartridges. I don't know if it is actually being done, but it is highly recommended." Letcher adds, "When you think about it, that is where all of the dirt is trapped, especially if you use a carbon block. That is where all of the fine dirt and sludge and junk that comes out of the storage tank will accumulate." Needless to say, it is a good practice to clean out that area during filter replacement.

Another thing to keep in mind is to be careful when handling the replacement filter. Any contamination on your hands can easily be transferred to the filter, and then to the drinking water. Many filters come sealed to prevent contamination. It is a good practice to remove only that part of the wrapping necessary to screw the filter into the housing. After it's installed, you can remove the rest of the wrapping being careful not to touch the filter. This helps prevent contamination to the filter that may be caused by touching it with your bare hands.

Leak check and flush

After re-assembling the filter you are almost done. The final things to do are to perform a leak check and flush. The leak check is pretty straightforward. You want to ensure all the connections and seals are secure and not leaking.

But something that may be overlooked is to perform a flush of the system. The purpose of flushing the system is twofold. First of all, it purges the system of any air bubbles. Secondly, it removes the fine carbon dust that is inherent to carbon filters. This will make sure that first glass of water that is poured out of the faucet doesn't look grey and cloudy. McLeod adds, "An additional function of the purging process is to activate the precoat in our GY filters. While purging, you are actually activating the precoat so it coats on to the septum material." Regardless of what type of filter you have, it is good practice to purge the system after filter installation.

Taking it to the next level

In some cases, an operator may need a higher level of filtration than just filtering out particulates and removing bad odors and taste. There may be concerns with other forms of contamination, particularly micro-organisms such as viruses and bacteria. This could be either from the water sources where the tanks are being filled or from stagnation in the tanks themselves. In this case, ultraviolet (UV) filtration systems are used.

Ultraviolet radiation is high energy light. The UV spectrum ranges from 40 to 400 Nanometers (nm), with the most effective spectral region for filtration being between 250 and 265 nm. In an UV system, water passes through a filtration module where mercury arc lamps generate the UV radiation. The radiation scrambles the DNA of any micro-organisms present in the water. The DNA molecules in the nucleus of the organisms absorb the UV radiation. As a result, their DNA is scrambled, either killing them or rendering them harmless to humans.

Keeping it effective

Since UV systems rely on UV light saturating the micro-organisms at the proper intensity, there are several factors to keep in mind to ensure the system is working at peak efficiency.

First of all, the water must be filtered prior to entering the UV filtering chamber. An UV filter relies on particulate filtration to remove contaminants prior to entering the UV chamber, ensuring the water is clear allowing full penetration of the UV radiation. So all the issues regarding maintenance of canister filters are just as critical in UV applications.

Regular maintenance of the UV filtration unit is also required. Rick Steadman, communications manager for International Water-Guard International, explains, "The life of the UV unit is approximately 1,000 gallons. We recommend operators change them out annually. The reason we say that is because even though the lamp itself may be strong, if the water you run through there is particularly bad, and if the canister filter doesn't get all of that, then you will get some clouding of the quartz sleeve that separates the lamp from the water. And if that gets cloudy, then the UV is not getting through."

Some of the UV filtration units that IWG manufactures have integrated monitoring systems to measure the efficiency of the lamp. In this case, regular inspection of the system during maintenance checks will ensure proper operation.

This article has covered some basics on water filtration. For more information on water filtration, or to see if a particular system is right for your application, you can contact the filter manufacturers. In addition, most completion facilities should be able to address any questions concerning water filtration applications for your aircraft.

Additional ReSource
International Water-Guard Industries Inc.
(604) 255-5555

Pentair Water Treatment/Plymouth Products
Toll Free (866) 873-7506
International (920) 457-9435

About the Author

Joe Escobar