FILTERING WATER

Greetings Bloggers-
In the previous 3 articles we covered a lot of ground. I know that the information provided so far has not been in that much detail and for that I apologize. My hope is you have taken the time to review the links provided and maybe have done a little research on your own. This fourth article in the series will focus on the heart of our discussions so far. That is, how can we remove or neutralize unwanted contaminants. We know that there are many contaminants that may be found in water. We also know that these contaminants can change from day to day and from location to location. Our goal is to be able to process water from normally available sources and have aesthetically pleasing water that is also safe. So, let’s get started.

There is a huge array of water filters available to us today. Some are very small while others may require a crane to move. There are systems that fit under the sink, gravity filters that set on a kitchen counter, systems that connect to a faucet and others that can be placed on a showerhead. Other configurations are designed to be used as an entry filter for all of the water entering the RV. Filters are made from glass, membranes, ceramic, paper, sand, charcoal or carbon and other media. There are thousands of filters on the market produced by hundreds of companies. Some processing methods are good while others are not. It is not possible to cover each and every potential method or system in this short article. For the most part, there are just a handful of processes that are worth a hoot. One of the very few we have researched and found to do a decent job is produced by Doulton, USA. I consider Doulton my main competition. Their filters are produced using high quality materials and they back up their claims with laboratory test reports. Very few companies are willing to share lab results, if they even have any.

You may see reference in some advertising to the National Sanitation Foundation, or NSF. The NSF is a Not-For-Profit testing laboratory similar to Underwriters Laboratory. It has become the authority for many consumer products, including water processing and filtration. If a product passes their tests, they will allow the manufacturer to state they are “NSF Tested”. It is a very expensive program that not all water processing system producers can or will invest in. The test protocols developed by NSF are used by many other test facilities, leading to statements like “Tested To NSF Standard 42” or something along that line. The following is a synopsis of two test protocols we are interested in.

NSF Standard 42

Test standard for aesthetic claims such as color, taste and odor. Also tests for particulate matter. One of the more important test parameters is for reduction of chlorine and chlorination byproducts such as trihalomethanes that are known carcinogens. There are three different classes of effectiveness for chlorine reduction. They are:

Class one - Reduces chlorine by 75 - 100%.
Class Two - Reduces chlorine by 50 - 74%
Class three - Reduces chlorine by 25 - 49%

Water may appear cloudy at times, caused by particulates. NSF Standard 42 tests for the reduction of particulates by particle size. The filter media can then be ranked. The categories are:

Class One - 0.5 – 1.0 microns
Class Two - 1 – 5 microns
Class Three - 5 – 15 microns
Class Four - 15 – 30 microns
Class Five - 30 – 50 microns
Class Six – Larger than 50 microns

NSF Standard 53

This test standard applies to those contaminants that are considered as health hazards. This includes pathogens (bacteria, virus, cysts), and heavy metals such as lead. Standard 53 also tests for Volatile Organic Chemicals (VOC’s), Total trihalomethanes (TTHM’s), turbidity and several chemicals found in agricultural or industrial applications.

Other NSF Test Standards of Interest

There are NSF test protocols for ultraviolet systems (Standard 55), reverse osmosis (Standard 58) and distillation (Standard 62), among others. You will find detailed information regarding these test protocols and many others on the NSF website.

The better filter producers will publish lab reports indicating the effectiveness of their product. Our system was tested by a certified test facility and we meet the requirements of Standard 42 for chlorine Class One and particulate Class One. We also exceed the requirements for Standard 53 for the contaminants we tested for. Many companies that market some type of water filter for RV use employ slick advertising that can be misleading. I see a lot of statements used like “Our Filter System Addresses the Following Concerns..” then they display a list of contaminants. Now, what does that mean? Do these contaminants have a mailing address? Darned if I know, but to address something does not indicate to me whether the processed water is any safer or better than raw water. Another marketing approach is to use words like “reduces” this or that. There is no indication how much of a reduction may take place. Even an old handkerchief will reduce or remove some contaminants. Sorry, got distracted there for a minute but misleading advertising really irritates me.

As stated previously, when you travel in your RV you may be faced with very inconsistent source water. Every time you hook up to a new water supply you should expect the water chemistry to be different. It is always a good idea to ask when checking in, where the park water comes from. Is it municipal or from a private source. You may also ask what testing has been done, when it was done and what the results were. The park should be happy to provide this information. These questions may not give you much assurance that the water is good or bad at that moment. It may indicate the level of concern the park management has. Let me state once again that potable water we consume here in the United States is generally safe. However, as my mother used to say, an ounce of prevention is worth a pound of cure.

In any event, let’s talk about what processes are available. There are essentially two ways of interest to us as applied to RV use. They are point-of-use (POU) and point-of-entry (POE). POU means filtering water inside the RV, probably via a third faucet at the kitchen sink from a filter unit under the counter. This may serve your purpose, I don’t know. The best method we believe is point-of-entry, where all of the water coming in to the RV is filtered. Then we can have good water at all of the outlets. Bathing or brushing your teeth with unfiltered water is not good. Unfiltered water can also damage the valves, plumbing and appliances within the RV.

Let’s back up a little and define what we want to do with our water. Our goal is to be able to have water in our RV that is consistently high quality without much regard for the actual source. We have found that due to the peculiarities of filter capabilities there is a minimum of two steps required to process water for consumption. We want to 1) clean the water of particulates and debris by pre-filtering, and then 2) purify it by removing soluble contaminants via a final or polish filter.

Generally speaking, it is difficult to accomplish both steps using a single filter. Filter media designed to remove particulates are not very effective in removing solubles. Conversely, a media that is good at removing solubles has limited ability to remove particles because the media will become clogged in a short period of time. In the near future it may be possible to accomplish this two-step process using just one filter. We are presently testing a single filter that shows great promise in performing both steps. The technology for this unit is just coming to the market. We hope to have this new technology lab tested very soon. At the other end of the spectrum I have seen arrangements using up to five separate filters, each one designed to remove specific types of contaminants.

Keep in mind that we need a flow rate of approximately 2.5 gallons per minute to service the RV. Flow restriction has to be part of the equation. Flow rate is reduced proportional to the level of restriction we impose in the filtering process. The tighter the filter, the less throughput it allows. So, we have to balance our flow requirements to the amount of work we want the filtering process to do. If you presently use a filtration system and the water flow out of it is as high as the flow rate going in, you are probably not getting much filtering.

So first we need to clean the source water by pre-filtering it. By cleaning I mean removing the particulates that can sometimes make water cloudy. Cloudiness is caused primarily by dirt, silt and debris particles. For our discussion here we will refer to this condition as TURBITY. Turbidity is measurable and, as discussed in a previous article, is expressed in Nephelolometric Turbidity Units or NTU’s. The EPA limit for municipal water turbidity is 1.0 NTU. The technology in our pre-filter typically reduces turbidity to .01 NTU. This removal process will also trap pathogens that may be present. The main reason we want to clean the water first is to protect the second or final filter from clogging. A proper pre-filter should have a huge dirt holding capacity. Most filters appropriate for final filtration have very little ability to hold particulates.

Cleaning or pre-filtering our water is relatively simple. A good quality sediment filter that will remove particles down to 1.0 micron or less is a good starting point. Most filters on the market are flow restrictive at this pore size. Filtering technology is available today that will remove particulates as small as DNA. Our pre-filter has this technology. This is very high-tech stuff and of course there is a price to pay for it. Our pre-filter is manufactured to our specifications and a technical discussion of the incorporated technology can be found here. This prefiltering step is essential for just about any purification process you may choose. For the purposes of this article, purification means the removal of other undesirable elements such as harmful chemicals, metals and other soluble constituents the cleaning process cannot remove.

The second step, purification, is a topic that has led to many discussions over the years. Some folks swear that reverse osmosis (RO) is the only way to purify water. I agree that it can be effective in removing particulates but does little to remove solubles. Many folks do not understand that RO cannot remove soluble contaminants. RO is also slow and wastes a lot of water for back flushing. Boiling can be good and bad. It will kill the living organisms but at the same time it concentrates other contaminants. Also, I personally have an aversion to ingesting any little dead bodies that may be present.

Distillation is a good purification process and will remove many contaminants but where in the world can you store a boiler and condenser in an RV? Distillation is slow and uses a lot of energy. There is also a lot of controversy about the health effects of drinking distilled water. Go to Distilled water for more information on this.

Chemical treatment like chlorination or iodine may kill some water-borne living organisms but does not remove the dead bodies and has no effect on soluble contaminants. Chemical treatment also has little effect on pathogens that have a protective shell such as Cryptosporidium.

Ultra Violet or UV is yet another treatment method. Water is passed through a chamber that has a special UV light bulb. This process kills some organisms with high doses of radiation. This method requires electricity and a fairly high maintenance schedule. It also is not capable of removing any contaminant.
Another treatment process that has become popular is Kinetic Degradation Fluxion, or KDF. This patented process has the potential to remove or control many contaminants through a molecule exchange principal. KDF is a copper-zinc compound that uses redox (oxidation/reduction) to remove or modify soluble contaminants like chlorine, hydrogen sulfide and heavy metals from water. The process also has a mild anti-bacterial, algaecitic, and fungicitic effect and may reduce the accumulation of lime scale. KDF is a granular substance that has little effect on pathogens that travel in an oocyst stage.
In our research we determined that the best way to purify water was by using a second or polish filter made with activated carbon. Carbon has some very interesting properties that seem to be tailor made for filtering water. When properly manufactured, it displays very high adsorptive properties making it perfect for removing soluble contaminants from water, such as organic chemicals (especially those that are responsible for odor, color and taste) along with other organics like chromium, arsenic, mercury, lead, chlorine and chlorination byproducts (Trihalomethanes, a family of known carcinogens) and a host of other constituents that are bad for us. The base carbon used is primarily derived from coal, peanut shells or coconut husk. The way it is made is the raw material is heated to a high temperature in the absence of oxygen and “cooked.” To activate the carbon, specialized oxidizing gas is then forced through the carbon at very high temperatures. Other additives may be used enhance the carbons ability to remove specific contaminants such as lead.

One gram of activated carbon can present a surface area equivalent to two tennis courts in size. That is a lot of filtering surface. Many of the less expensive carbon filters are nothing but a cellulose sheet that has been impregnated with a small amount of carbon dust. The better carbon filters are made with compressed carbon and are solid. It stands to reason that the more carbon in the filter, the better.

Many carbon filters are made with granulated activated carbon (GAC). Although this process is popular, GAC is loose within a container and has a bad habit of “channeling” during the filtration process. This channeling allows water to flow through without coming into contact with the carbon, greatly reducing efficiency.

To be effective, the carbon has to be in a brick or solid form and have very small pores that forces contact with the water. There are basically two ways to produce a solid brick filter. Some manufacturers mold the carbon dust, making one filter at a time. A binder is added to the dust to help hold it together. The binder, or glue, reduces the total exposed surface area, reducing performance. It is also difficult to control pore size in the molding process. Probably the most optimum carbon filter is made through an extrusion process. Fine carbon dust is forced through a forming die at extremely high pressure, producing a continuous hollow-core “rod” of solid carbon (much like aluminum is extruded). This rod is very dense and structurally strong. The rod is then cut to whatever length is needed and incorporated into the filter. This process insures consistent density throughout the filter, allows the greatest surface area and, if done properly, controls pore size. A well-designed extruded carbon filter can offer a pore size down to 0.5 microns or less. An informative web site on extruded, activated carbon can be found here. Our final filter is produced to our specifications using the extrusion process.

One major drawback to carbon is its limited ability to hold dirt and other contaminants. There is no room to hold dirt due to density. Using a carbon filter without properly pre-filtering the water will lead to premature clogging. There is another drawback to carbon that you may have heard about. Carbon is organic and bacteria love it. As the filter collects debris and contaminants it becomes a smorgasbord that bacteria can live on. Given an opportunity, bacteria will colonize and thrive within the carbon. So at some point this process may become counter-productive. The carbon will either become clogged with bacteria and debris or will breakdown and allow large amounts of contaminants to pass. To answer this problem, some manufacturers are now adding anti-bacterial components such as silver to the carbon to control this growth. There has not been much research into the long-term ramifications of silver additives, so I am somewhat skeptical. During our research we determined that a much better approach is to remove bacteria during the pre-filtering stage, therefore bacteria never have the chance to invade or colonize the carbon. Our RVF-1 system does just that.

We have not covered all of the potential methods to filter water. There is a lot of information on the Internet regarding these and other technologies if you care to investigate further. We spent years researching, talking about and testing various water process methods. I have been like a dog on a hunt looking for the best way to process our RV water. This series of articles gives you the essence of what I discovered.

So, there you have it. I have tried to not turn these articles into a sales campaign for our filters. My purpose has been to offer a small amount of information for you to consider and just maybe help keep you safe. I do invite you to review our website at http://www.covesystemsinc.com/ for further information.

If you have any questions, let me know. I would very much like to hear from you. Whatever you are doing now or decide to do in the future about the water you use, remember that it is imperative you take control of the situation. Do not simply assume that the water you use is okay. That is like playing with bumblebees. And I can tell you for sure that when your first cup of coffee in the morning tastes like coffee, not dead fish, the day will be much better.

There is one more subject I want to discuss with you in the next and final article. That is taking care of the RV fresh water system and managing RV water. When you purchased your RV, the salesman probably said something like, “here’s where yah hook up the hose”, at which point he lowered his voice. Being a good salesperson, he or she offered no more information than that necessary to make the sale. So, we will review some simple steps we can take to keep the water system clean and free of contaminants. Oh yes, that chemical formula shown in the box at the beginning of this article is for methane gas. A substance that my wife has accused me of producing in great quantity. Happy Trails.

Jim Worden
Sevierville, Tennessee
rvwater@aol.com