GAC Filter Project
Additional GAC Filter Project Complete
Last week, the newest granular activated carbon, or GAC, filter installation at the Plainfield Township water treatment plant was officially completed and is ready to go for summer.
Work on the latest round of modifications to convert three additional water filter beds to accommodate GAC to filter out PFAS compounds from municipal drinking water began in April. This brings Plainfield Water’s total GAC filtration capacity up to 12 million gallons per day, or mgd.
Converting the additional filters to GAC allows the plant to meet summer peak demand when lawn sprinkling and other activities can double or nearly triple demand up to 10 or 11 mgd.
The initial GAC installation was funded by a grant from the state of Michigan to study the effectiveness of GAC filtration to eliminate PFAS compounds in municipal drinking water. Extensive testing since the filters were converted has indicated the GAC filtration is highly effective in eliminating PFAS while still effectively eliminating bacteria, pathogens and other undesirable elements from our drinking water. (June 6, 2019)
Further information can be found on the Michigan PFAS Action Response Team website here.
State Testing Confirms Plainfield Municipal Water Remains Free from PFOS and PFOA
Additionally, the total for all PFAS compounds tested was just barely above detectable levels at 2 parts per trillion, or ppt, a significant improvement from the test the state took in May 2018. The May 2018 test occurred prior to the installation of granular activated carbon, or GAC, filtration at the water plant, which has proven very effective for removing all PFOS and PFOA compounds and greatly reducing other “short-chain” PFAS compounds as well.
These test results are consistent with the monthly testing Plainfield Water Department has conducted since the installation of GAC filtration as a portion of the pilot project funded by the state of Michigan.
As a part of the pilot project, Plainfield has installed GAC filtration using two different varieties of activated carbon compounds. Two filter beds totaling 4 million gallons a day, or mgd, of filtration capacity were outfitted with GAC that specifically targeted the PFOS and PFOA compounds. Health experts indicate these two “long-chain” PFAS compounds present the greatest health risk in drinking water. While Plainfield has found this variety of GAC to be completely effective in eliminating PFOS and PFOA from drinking water, it may not capture all other PFAS compounds.
The EPA has established a health advisory guideline of 70 ppt for PFOS and PFOA combined in drinking water. However, no health advisories have been established at this point for other PFAS compounds, commonly referred to as short-chain PFAS compounds.
The second type of GAC filtration is better suited to eliminate all types of PFAS, but may have a shorter effective span due to this approach. Monthly testing has indicated that this variety of GAC is completely eliminating all types of PFAS compounds, as well as the two long-chain varieties. Plainfield installed this type of GAC in three filters totaling 5 mgd of filtration capacity in 2018 and is nearing completion of another 3 mgd of capacity this month for a total of 12 mgd of GAC filtration between the two varieties.
The pilot project, funded by a $750,000 grant from the state of Michigan, is intended to test the effectiveness as well as cost-efficiency of converting traditional water filtration methods to also address PFAS contaminants. In the first year of the project, the GAC has proven very effective in treating the low levels of PFAS in the groundwater entering the Plainfield water plant. However, ongoing monthly testing funded by the grant will also test the longevity of this approach to indicate how cost-effective it is in comparison to other approaches to combat PFAS contaminants.
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