By Tina Fischer, CWS-VI
Arsenic in groundwater. How many times have you seen or read that headline? There is no doubt that arsenic has become a common household term used not only by high school teenagers that are studying the periodic table for the first time but also by moms and dads who have long forgotten their high school chemistry class.
In the last 10 years, arsenic has made headlines for various reasons. Most deal with human exposure and its associated risks.
To recap some of the recent headlines, arsenic is present in natural deposits in the earth. It can enter drinking water supplies from natural deposits or from agricultural and industrial practices.
Being that arsenic is odorless and tasteless, many consumers do not worry about arsenic as a contaminant. However, as noted from the US EPA website, “Non-cancer effects can include thickening and discoloration of the skin, stomach pain, nausea, vomiting; diarrhea; numbness in hands and feet; partial paralysis; and blindness. Arsenic has been linked to cancer of the bladder, lungs, skin, kidney, nasal passages, liver, and prostate.” Thus, if present in a water source, arsenic should be treated in a serious manner.
As consumers become more and more savvy, it becomes increasingly important to certify drinking water treatment equipment for any and all reduction claims that are made. While consumers likely do not fully understand certification, it is impossible to argue the fact that when buyers enter retail stores (such as Wal-Mart or The Home Depot), the water filtration aisles are packed full of boxes with certification logos all over them.
The fact is, while consumers may not understand all the details and behind-the-scenes facts that go into product certification, they do understand the difference between products that carry a certification mark to ones that do not. In a world where more is always better, that mark carries a lot of weight.
Arsenic reduction systems have been around for many years, both POU and POE. Most commonly, RO systems have been tested and certified for the reduction of arsenic. However, a handful of carbon-based products are tested and certified for arsenic reduction, as well.
Certainly, while RO is a good option, there lies a problem with getting RO treated water to all taps in the house. The most common reverse osmosis units typically do not run at flow rates to support a whole house. Those systems that are made for whole-house applications too are extremely costly and are not very affordable for the average consumer.
To provide a more feasible means to reduce arsenic contamination than RO, media manufacturers have taken the bull by the horns and developed specialized media that has the ability to reduce arsenic in water. A very common use for this media is actually for the large-system market.
Municipalities also contribute to ensure that water they provide to consumers is as close to arsenic free as possible. Manufacturers are now tailoring the media for residential applications.
POU products are the most common available for residential use to reduce arsenic contamination. For those who live in areas where arsenic contamination is an issue, however, a POU system would not provide treated water throughout the home. It would only provide reduction at the one tap to which it is connected.
To further complicate the issue, some homes are not supplied with municipally treated water and rely on personal wells to carry water to their faucets. Some consumers may get municipally treated water but still prefer to have complete control over their water treatment capabilities.
Therefore, the only other option is a POE system, which would offer a great option for complete assurance that all the water that is consumable is treated to reduce arsenic. It comes, however, at a very high price.
The problem manufacturers and consumers alike face is the economics behind manufacturing, testing and purchasing/selling a POE filtration system that has the ability to reduce arsenic. In order to have a POE system tested and certified according to the NSF/ANSI 53 standard, there are a couple things to consider.
Arsenic occurs in two forms; pentavalent and trivalent. Depending on the water source, arsenic may be present in either or both forms. Furthermore, due to the variability in levels of arsenic found in water, the standard allows for manufacturers to choose between an influent challenge of either 0.3 mg/L or 0.050 mg/L.
In either case, the allowable effluent level is 0.010 mg/L in product water. In addition to the options available within the standard, the standard requires that arsenic reduction testing be conducted with both pH 6.5 and pH 8.5 water.
Typically, trivalent arsenic is more difficult to remove. However, it can be converted to pentavalent arsenic. In order to facilitate the conversion, detectable free chlorine residual must be present. When the oxidant such as free chlorine is present, it has been demonstrated to effectively convert trivalent arsenic to the pentavalent form.
Even though this conversion is possible and testing for pentavalent arsenic only is acceptable, the most marketable system would be tested for both trivalent and pentavalent arsenic. To do so would require a total of four reduction tests to be performed (trivalent at 6.5 pH, trivalent at 8.5 pH, hexavalent 6.5 pH and hexavalent 8.5 pH).
Beyond the number of tests, increased costs are incurred due to the nature of the testing because it is a health claim. When a system is tested to reduce a health claim, it is tested to either 120 percent (if the system has a performance indicator) or 200 percent (if the system does not have a performance indication device).
In addition, since arsenic reduction systems are usually constructed with an exhaustive media and are being used for whole house applications–where significant amounts of water are flushed down toilets or used in dish or clothes washing–the capacities of these whole house systems are typically upwards of 50,000 to 100,000 gallons (189,270 to 378,541 liters). These two facts combined mean that the system will be required to be tested for 60,000 to 200,000 gallons (185,829 to 619,431 liters).
A test with that much water could run for months depending on the flow rate used for the testing. Any test that takes months to run is going to increase the cost of the test significantly, compared to a POU product that may only be tested for a few days to a few weeks.
The good news is that currently there is a task group working toward an end goal to find a way to allow more systems to enter the market by performing the certification challenge testing in a significantly more economical manner. The group is working on a column-based testing protocol for perchlorate specifically.
It is assumed that these theories and concepts will be transferable to not only arsenic but also many other health claims. The column-based testing approach will allow for the physical tests to be completed on a much smaller scale while replicating the treatment technology processes which would greatly reduce the costs for the testing. This savings occurs because the amount of water and days of running the test will presumably be significantly reduced.
Certified POU residential water treatment systems with the ability to reduce arsenic or other health claims are common and affordable. Certified POE systems with the same capabilities are few and far between.
Costs that are incurred when attempting to obtain certification are substantial. Hope is on the way to alleviate some of the financial burden in getting these types of whole house systems certified.
At this time, POE options for the reduction of arsenic are severely limited. Due to the high costs of testing, WQA has only certified one family of whole-house systems that have the capability of reducing arsenic.
For more information regarding the certification of your point of use or point of entry arsenic reduction system, contact Melissa Tonsor at the Water Quality Association at (630) 505-0160 x527.
About the author
Tina Fischer CWS-VI, Product Certification Supervisor for the Water Quality Association’s Gold Seal Program, has worked for over eight years to develop Gold Seal as an organized ANSI and SCC accredited program. Fischer and Product Sales Manager Melissa Tonsor, CWS-VI, can be contacted at WQA to provide additional information on obtaining all component or system certification. Tina can be reached by telephone (630) 505-0160 ext. 533, facsimile (630) 505-0752 or email [email protected].