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NSF/ANSI 53 Certified Water Filter Efficacy in Benton Harbor, Michigan
Citation:
Tully, J., D. Lytle, M. Schock, V. Bosscher, AND S. Shilling. NSF/ANSI 53 Certified Water Filter Efficacy in Benton Harbor, Michigan. AWWA Water Quality Technology Conference, Cincinnati, OH, November 13 - 17, 2022.
Impact/Purpose:
A POU and pitcher filter efficacy study was conducted in Benton Harbor, MI homes due to concerns about elevated Pb levels beginning in 2018 and limited similarities (i.e., phosphate treatment) to Newark, NJ where Pb-phosphate nanoparticles had been observed. All samples from properly certified (NSF/ANSI-53) and operated filters included in the study (199 locations) were found to reduce Pb to below the certification standard of 5 ppb. Concurrent particulate analysis from a smaller subset of homes did not find discrete Pb-phosphate nanoparticles as a result of the blended phosphate treatment. Field observations during this study highlighted the importance of public education surrounding filter installation, replacement, and use.
Description:
The City of Benton Harbor, MI, initially exceeded EPA’s Lead and Copper Rule (LCR) lead action level (AL) of 15 ppb in 2018. The system continued to exceed the Pb AL during five additional monitoring periods from 01/2019 to 06/2021, and the 90th percentile decreased to the AL for the sampling round ending in 12/2021. In response to the AL exceedances, the Michigan Department of Health and Human Services (MDHHS) began providing the community with faucet-mounted point-of-use (POU) and pitcher filters certified by NSF/ANSI-53 for Pb reduction to reduce the level of Pb in the tap water in early 2019. Then in 03/2019, the City began adding a 70% orthophosphate and 30% polyphosphate blended corrosion-control inhibitor at a target residual of 1.5 mg PO4/L. After 1 year the treatment was changed to a 90% orthophosphate and 10% polyphosphate blend to achieve a 3 mg PO4/L residual in the distribution system. As a result of the City’s persistent drinking water difficulties, a Safe Drinking Water Act petition was submitted to EPA in September 2021 which laid out a list of proposed actions along with requesting a filter efficacy study be conducted by EPA’s Office of Research and Development (ORD). A study was designed by ORD to evaluate filter effectiveness (certified faucet and pitcher filters), and samples were collected between 11/9 – 12/17/2021 from a total of 215 homes, resulting in 199 properly installed and operated filter study homes. Several efforts were made to sample higher-Pb challenge water, including targeting homes with lead service lines and, for the latter part of the study, encouraging longer stagnation times and collecting 7th and 8th liter filtered and unfiltered samples. Lead in the unfiltered water samples associated with properly operating filters ranged from below the laboratory reporting limit (<0.5 ppb) to 77 ppb. None (0%) of the filtered water samples exceeded the NSF/ANSI-53 certification standard of 5 ppb Pb. Ninety percent (90%) of the filtered samples were below the reporting limit for Pb, and the highest filtered water Pb concentration measured in the sampling pool was 2.5 ppb. While EPA was in the field sampling teams observed current filter use, including that some residents did not understand how to use the filters properly, particularly the faucet mounted POU filters. These filter study results combined with a concurrent particulate analysis from a smaller subset of other homes within the community confirmed what was expected (based on water quality), that Pb containing particles were associated with larger masses of material. This lack of discrete Pb-phosphate nanoparticles added evidence that the blended phosphate treatment was not contributing to Pb levels through the formation of mobile Pb-phosphate nanoparticles. This case study highlights the effectiveness of NSF/ANSI-53 certified filters to reduce Pb in drinking water and the importance of public education surrounding proper filter use/maintenance and messaging.