Monitoring Advanced Hydration Station (AHS) Water Quality in Flint, MI, School Buildings: Field Grab Sampling and Filter-Based Lead Assessment

Abstract

School drinking water lead exposure remains a public health concern. In addition, time-variant lead concentrations pose challenges to monitoring practices. This study evaluates the lead (and, for some experiments, bacterial) removal performance of advanced hydration stations (AHS) with membrane filters, activated carbon block filters, and LED UV disinfection in Flint, Michigan. Laboratory challenge testing and more than 400 grab samples were collected from influent and effluent water from over 70 field-deployed AHS units during three sampling campaigns in 2022 and 2023. Our study confirmed that AHS units effectively removed lead. The median influent lead concentrations ranged from 6 to 14 μg/L, with 53% of samples exceeding 10 μg/L. Lead levels in effluent water were almost all below the detection limit (98% of samples). Effluent bacteria concentrations monitored during the first field sampling campaign in 2022 were all below detection, and removal during challenge testing were >2.6 log reduction. A subset of filters (n = 21) from those harvested in July 2022 were acid-extracted to assess the total accumulation of lead. This information, along with the cumulative volume of water processed, was used to calculate a volume-averaged lead concentration that represents avoided lead exposure and identifies potential hot spots of lead release to prioritize remediation activities. The outcomes of this monitoring campaign demonstrate the effectiveness of the AHS units at removing lead and bacteria, and the importance of using filter-based monitoring to inform AHS maintenance and identify upstream sources of lead.