One of the primary purposes of Graver Unfiltered is to uncover interesting or newsworthy information relevant to the wide range of applications where filtration plays an important role. From pharmaceutical manufacturing processes to industrial wastewater treatment to food and beverage production, proper filtration is essential for sound economical considerations and rigorous safety standards. When those considerations and standards shift, filtration concerns must be revisited and, in some cases, new solutions applied. Recently, this blog has covered one such application—water treatment, and specifically, drinking water filtration—with filtration technology designed to address a contamination issue that has undergone new regulatory controls and which continues to find its way into the news cycle: arsenic.
Arsenic has been identified by the World Health Organization (WHO) as one of the ten toxic chemicals or groups of chemicals of major public health concern. Arsenic and inorganic arsenic have been established as
a Class 1 human carcinogen by the International Agency for Research on Cancer. The primary route for human exposure is contaminated drinking water. Chronic exposure can cause skin lesions, diabetes, cardiovascular diseases and other ailments. Acute exposure to high concentrations can lead to muscle cramping and even death. Cancer caused by arsenic is difficult to detect, as symptoms can take 10 to 20 years to manifest.
In 2000, WHO decreased its limit for arsenic in drinking water from 200 ppb (parts per billion) to 10 ppb. Shortly after, other regulatory organizations adjusted their limits as well, including the U.S. EPA, the Bureau of Indian Standards, the European Commission, and the National Health and Medical Research Council, Australia. Some countries still have higher limits, such as Mexico which has a limit of 25 ppb. In the U.S., once a region has tested below the limit of acceptable contamination, its governing bodies can wait another three years before testing in order to control costs, or in the words of the EPA: "...balance the current understanding of arsenic’s possible health effects against the costs of removing arsenic from drinking water”.
One example exists in the case of drinking water from Swale Brook Well in the Tunkhannock Borough of Pennsylvania, the levels were just under the legal limit at 8 ppb of arsenic as of July 2018. The remaining three entry points for drinking water in Tunkhannock had levels of 0 ppb in 2018. Since 8 ppb is less than the maximum contaminant level of 10 pbb, it's been announced that there is no cause for concern—and no need for costly treatments. But the acute discrepancy may not signal all is "well". At Swale Brook Well, erosion of natural deposits, runoff from orchards, and runoff from glass and electronics production waste resulted in the arsenic contamination. Some may wonder if levels will go above the limit by 2021 when testing will again be required.
And just last month, the Environmental Protection Agency (EPA) weakened safeguards for coal ash piles and sites where coal ash is placed on or beneath the ground. The change encourages greater use of toxic coal ash as a filler in construction and landscaping by removing all volume restrictions for such waste projects. The proposal allows unlimited volumes of coal ash and there is no required notification to the public that such projects are occurring and no requirement to share demonstrations with the public unless directly asked. Coal ash contains deadly toxic substances including arsenic, as well as cadmium and chromium, and neurotoxins such as lead and lithium, which have polluted air and water at hundreds of coal ash dumpsites across the nation.
As it is the responsibility of all public water systems to ensure that the water being supplied to their customers meets both the primary and secondary maximum contaminant levels, testing must not lapse as the cost of removing arsenic can far outweigh the costs of monitoring it. The costs of treating arsenic contamination can be very high, and there are many technologies used in reducing arsenic to below regulatory levels. In communities that use wells to remove arsenic from groundwater, coagulation-flocculation is the most widely used method. However, this method generates a significant amount of hazardous sludge wastes.
Increasingly used for arsenic removal are membrane technologies like reverse osmosis and nanofiltration. These techniques have high removal efficiency but the costs are relatively high and may not be suitable for large-scale processes. As well, the concentrated effluent in the reject leaves a waste stream that can be released into the environment.
Adsorption is often a preferred method because of its affordability, low energy, high efficiency, ease-of-operation and manageable waste. In the last 10 years, advances in material science and chemistry have provided new and novel adsorbents with unique size-shape and surface-active properties which selectively remove arsenic from aqueous sources. Gaining attention among adsorbent material is activated carbon due to its high surface area, well-developed super-microporous structure, relatively low cost, and the presence of a range of surface functional moieties.
For more information on these and other technologies, feel free to read this recent Talking Tech article in Water Quality Products with contributions by Graver Technologies own Nichole Pennisi and Joshua Mertz and explore our MetSorb™ removal products.