A 28-year-old woman from a rural village in Uttar Pradesh presents with a 3-week history of progressive neurological symptoms: tremor, ataxia, and personality changes. Her family reports that she has been drinking water from a hand pump in their village. On examination, she has coarse tremor, dysarthria, and emotional lability. Laboratory investigations reveal elevated urinary mercury levels (45 µg/L; normal <5 µg/L). The village water supply was recently found to be contaminated with mercury from an upstream industrial discharge. What is the most appropriate immediate intervention to prevent further cases in this community?