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Pure Water Occasional, October, 2022
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Greetings from Pure Water Products, the Pure Water Gazette, and the Pure Water Occasional.
In this Almost Halloween Occasional, there are articles about the great variety of carbon filter cartridges available, how turbidity is measured, residential treatment of PFAS, the deplorable state of America's water pipes, the renaming of Katalox Light, and how showering can be dangerous.
And, as always, there is much more.
Thank you for reading and sincere thanks from Pure Water Products for your continuing support. We consider our greatest asset to be the many faithful customers who have kept us going over the years. We really appreciate your support!
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Thanks for reading!
Please visit the Pure Water Gazette, where you will find hundreds of articles about water and water treatment.
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The Great Variety of Carbon Filters
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We just counted.
In the “Cartridge Menu” at purewaterproducts.com there are more than fifty separate carbon filter cartridges, and that’s just in the four standard sizes. These range from carbon blocks to granular carbons, many with specialty additives like calcite and KDF. There are coconut shell carbons, bituminous carbons, and lignite carbons. Additionally, there are carbon filters enhanced to remove lead and cysts, to prevent scale buildup, to inhibit bacterial growth, to remove fluoride, to reduce tannins, and to raise pH. There are carbon filters that target VOCs and others that offer fantastically long and effective chlorine and chloramine reduction.
In addition, there are “proprietary” carbon filters for a number of brands (Microline, Hydrotech, for example), inline carbons (from Pentair and Omnipure), aftermarket knock-offs (Multipure), and several ceramic candles with carbon cores.
Filter carbon is the central core of most modern water filtration systems. For some 90% of the water contaminants monitored by the EPA, carbon filtration is the preferred treatment. We hope you’ll look over our carbon collection. Our “Cartridge Menu” offers extensive information on all the carbon filters that we sell, including pictures, performance summaries, and links to manufacturers’ brochures.
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A Common Sense Approach to Residential PFAS Treatment
by Emily McBroom and Gene Franks
Most of the information now available about how to remove PFAS from water focuses on the gigantic carbon filters made to treat the millions of gallons of water per day required by cities. Also mentioned are the very small residential drinking water filters, mainly carbon filters, that have received NSF certification for PFAS removal from drinking water.There is a lot of confusion about the residential applications that fall between the gigantic and the tiny.
Here are some things to consider about residential applications for PFAS reduction.
Consensus is that three treatment strategies work with PFAS: carbon filtration, reverse osmosis, and ion exchange. Of these, carbon (GAC) filtration seems most practical for municipalities. GAC and reverse osmosis both work well for residential users, with reverse osmosis an easy first choice for drinking water. One agency tested eleven separate undersink reverse osmosis units and found that they all removed PFAS well. Several pretty unassuming carbon filters have gained NSF certification for PFAS reduction.
- Those who recommend treatment equipment for residential applications almost always make an unfounded assumption that homes must use point of entry equipment, treating all the water going into the home. We find no convincing information to indicate that PFAS in water is anything other than an ingestion issue. According to the CDC’s Agency for Toxic Substances Disease Registry: “Studies have shown that only a small amount of PFAS can get into your body through your skin. Therefore, showering and bathing in water containing PFAS should not increase exposure. Washing dishes in water containing PFAS should not increase exposure.”
- For point of entry treatment, we found that almost all recommended treatments are simply scaled-down versions of the strategies developed for municipalities. Usually there is no rationale stated that would justify the sizing recommendation. Recommended sizes range from extra large to even larger. We found EBCT (Empty Bed Contact Time) recommendations for PFAS ranging from 6 to 16. Ten is a common recommendation. Using an EBCT of ten, to provide a modest service flow of five gallons per minute for a residential whole house filter for PFAS one would need almost 7 cubic feet of granular carbon. That’s a 21″ X 72″ carbon tank, or three or four 12″ X 52″ tanks installed in series, or five 10″ X 54″ tanks installed in series. One authority recommends “at least 200 pounds of GAC” for residential whole house treatment–a 7 cubic-foot filter array. That’s a lot of equipment to assure PFAS-free water for flushing toilets. The most commonly suggested point of entry system is for two 12″ X 52″ GAC filters installed in series, without regard to family size. This would provide an EBCT of 6 at 5 gpm.
- There is little information about PFAS performance for whole house sized carbon block filters, although carbon block units might offer the most practical PFAS whole house option. MatriKX coconut shell carbon blocks now all carry certification for significant PFAS reduction.
The Obvious Conclusions
Our advice to consumers is get an undersink RO unit. If you don’t want reverse osmosis, get a high quality undersink or countertop carbon drinking water filter with an ample amount of carbon, and service it regularly. Ignore PFAS as a point of entry treatment issue, but don’t drink water from the bathtub. Treat your drinking water well, and add a whole house carbon filter if you want to, but you don’t have to get a box-car sized filter that competes with the city water department because if your drinking water is taken care of, a little PFAS in the shower water won’t matter.
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Partly because of misleading advertising, there is broad misunderstanding about what "NSF Certification" of water treatment products really means. NSF certification is not necessarily a guarantee of performance. Certification of water treatment devices is done under a number of "standards," and only some of them involve performance. And who or what is NSF, anyway? For the answer to this and other persistent questions about NSF, please read "The Mysteries of ANSI/NSF Explained," on the Pure Water Gazette's website.
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America's Dirty Little Secret
Water Online writer Sara Jerome, in her article “Small Town, Big Water Problems,” says that in the small Louisiana community of Enterprise, the tap water is so bad “one woman drives 20 miles each way to do her laundry in another town.” The water situation in Enterprise illustrates a festering problem in the United States: Funding for infrastructure repairs and upgrades in small communities is hard to come by.
Jerome continues:
“Years of water system neglect means that the 250-or-so residents there are left with pipes that leak more than 70 percent of their water into the ground — all because they can’t afford to fix them,” CNN reported, citing John Tiser, resident and water board president.
But Enterprise is hardly alone.
“The EPA estimates $132.3B is needed to repair small water systems in America over the next 20 years. But, in 2017, only $805.7M was allocated to these systems — about 12 percent of the amount needed,” CNN reported.
Virginia Tech Engineering Professor and water expert Marc Edwards refers to it as America’s “dirty little secret.” He explains that oftentimes towns like Enterprise are stuck with aging infrastructure that they can’t fix, leaving few options for them to deal with complaints about dirty or contaminated water. Edwards received a nearly $2M grant to uncover water issues in towns like this.
When Edwards and a scientific team tested Enterprise’s water in 2017, they found bacteria, lead and other contaminants that exceeded EPA limits.
“The whole idea is, at the end of this, to come up with a model to predict which cities are likely to have problems,” Edwards said. “Which cities are most likely to have lead pipes, and not be following the rules, and then work with communities there to figure out if they do have a problem, then build algorithms for individual homeowners to protect themselves, from sampling to filters.”
It is important to point out that while “over 92 percent of U.S. residents who receive water from community water systems are supplied by water that meets health-based standards at all times,” the U.S. EPA estimates that over $743B is needed for water infrastructure improvements.
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‘World’s dirtiest man’ dies in Iran at 94, months after first wash
An Iranian hermit nicknamed the “world’s dirtiest man” for not taking a shower for more than half a century has died at the of 94, state media has reported. Amou Haji was reported not to have bathed with water or soap in more than 60 years, fearing it would make him sick. The Iranian, who lived in the southern province of Fars, had avoided previous attempts by villagers to get him clean. But local media say he finally succumbed to pressure and washed a few months ago, and became ill shortly afterwards and died in October of 2022. The Guardian.
Haji's demise shortly after bathing brings to question the almost universally accepted belief that regular bathing and good health go hand in hand.
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Manufacturer Changes Katalox Light’s Name to Katalyst Light
by Gene Franks
The popular iron/manganese medium that has been sold for a number of years as Katalox Light will in the future be called Katalyst Light. The German manufacturer, WatchWater, has given no explanation for the name change. One would assume a patent violation. If you buy Katalox and it comes in a bag or box labelled Katalyst, or if you buy Katalyst and you get Katalox, not to worry. Regardless of what the bag says, it’s the same material.
While we’re revising the product name on our website, we will also be changing the minimum backwash and maximun service flow recommendations for the filters we furnish that use Katalox/Katalyst. The manufacturer’s original recommendations were, to be blunt, way too good to be true, but we based our recommendations on them. The newer Katalox/Katalyst brochures have more realistic numbers and we are revising ours accordingly.
A Fool’s Errand
Sizing and setting up a backwashing filter for iron and/or manganese treatment is largely a guessing game. The more that’s known about the water being treated, the more accurate the guess can be, but in the end, it’s still a guess. There are simply too many factors that influence backwash and service flow requirements for a “one size fits all” sizing chart to work for everyone.
Manufacturers of iron/manganese products like Katalox (Katalyst) and Filox-R pass the sizing decisions on to the user of the product by providing only vague, generalized sizing information. The new Katalyst literature states the service flow capacity of the medium as 4 to 12 gallons per minute per square foot. (That is, square feet of surface area of the media bed. A 10″ diameter tank, for example, has a surface area of 0.54 square feet, while a 13″ tank has an area of about 0.92 square feet,) With Katalyst, therefore, the manufacturer is saying that if you use a 10″ tank you can treat a maximum service flow to your home of up to somewhere between 2 and 6.5 gallons per minute. The exact service flow capacity for the individual home depends on such factors as whether you are treating iron, manganese, or a combination of the two, if there are other competing contaminants in the water (like hydrogen sulfide), the pH of the water, the oxygen content of the water, and pre-treatment provided.
With backwash rate requirement, the big unknown (to most users) is the water temperature. Cold water backwashes a filter much more efficiently than warm water, so less backwash water is needed if the water is cold. Filox’s manufacturer states the backwash requirement between 16 and 23.5 gpm per square foot, depending on the water temperature–in other words, between 8.5 (cold water) and 12.5 gpm (warm water) for a 10″ filter tank. Other important variables, like the total contaminant content, enter the equation as an educated guess. Obviously, a more vigorous backwash is required to clean a media bed if the iron content of the treated water is 10 parts per million as opposed to one ppm.
The type of tank used also matters. We use Vortech tanks for most filters and assume, based on manufacturer’s data, that Vortech tanks increase backwash efficiency by at least 20%.
With that in mind, here’s how we are revising our Katalyst (Katalox) recommendations. The numbers are simply a guess based on the average of the high and low figures given by the manufacturer. For example, Katalyst recommends a minimum backwash rate of 10 to 12 gpm/ft2, so we used 11 gpm/ft2.
| Tank Diameter in Inches |
Maximum Service Flow–GPM |
Minimum Backwash Rate — GPM – With Vortech Mineral Tank |
Minimum Backwash Rate — GPM – With Standard Mineral Tank |
| 9 |
4 |
4 |
5 |
| 10 |
5 |
5 |
6 |
| 12 |
6 |
7 |
9 |
| 13 |
7 |
8 |
10 |
Charts like this are not a guarantee of performance. They should be used as a starting place. If your contaminant content is high, decrease the maximum service flow accordingly. If you are planning a filtration project, we can’t guarantee a perfect outcome, but we can help you make an educated guess at sizing. The more information you can provide about the water, the better the chance of a good outcome.
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Places to visit for additional information:
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Thanks for reading. The next Occasional will be out eventually--when you least expect it.
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