Prior research shows that there are disparities in drinking water quality that occur along sociodemographic lines. For some chemical contaminants, treatment processes beyond what is conventional are needed to improve drinking water quality, although these more advanced processes can be costly to implement and maintain. Here we examine disparities in the rate of implementation of such treatment technologies among a nationwide sample of US community water systems (CWS) with different sizes and customer bases. Our statistical analyses revealed that adoption of technology useful for removal of emerging contaminants among the largest CWS occurred at 7-8 times the rate of small and very small CWS over a 19-year period. We also observed lower adoption CWS that provide water to populations with higher proportions of non-Hispanic Black residents. We infer from these results that policy interventions to improve water treatment infrastructure among small CWS and those serving historically disadvantaged communities will be needed to address sociodemographic disparities in water quality.