Background: Millions of villagers in Bangladesh remain exposed to high levels of arsenic (As) from drinking untreated well-water even though the scale of the problem was recognized 15 years ago. Water treatment at the household-level has been promoted as a viable complement but few longitudinal studies of their efficacy using an objective measure of exposure have been conducted. Participants (N = 622) of a nutrition trial in Araihazar, Bangladesh were each provided with READ-F filters at the beginning of the study and encouraged to use them over the 6 month duration of the intervention. Well-water As, treated water As, and urinary As were monitored periodically during the trial and measured again one year after the trial ended. Results: The READ-F filters were initially well received and median urinary As levels for participants declined from 117 μg/L to 51 μg/L within a single week. However, median urinary As levels gradually rose back to 126 μg/L by the end of the trial. Fifty filters were replaced over the course of the trial because of insufficient As removal or reduced flow. With these exceptions, most of the treated water met the WHO guideline for As in drinking water of 10 μg/L. One year after the nutritional trial ended, 95% of participants had abandoned their filter citing inconvenience as the primary reason. At that time, median urinary As levels for 10 participants who had switched to a nearby low-As well had declined to 63 μg/L. Conclusions: Participants were probably no longer using the READ-F filter long before the 6 month nutritional intervention ended despite claiming that they were using them. Household-level treatment is likely to continue to play a minor role in the effort to reduce As exposure in Bangladesh. Understanding the limitations of such expensive interventions is important for future policy regarding As mitigation.