CM3.2-3 | CM3.2-3 | Safe Water and Waterborne Disease — Summary & Reflection

KEY TAKEAWAYS

Safe and wholesome water is defined by freedom from pathogens, harmful chemicals, and objectionable physical qualities. Key points:

• Source hierarchy: piped treated supply > protected well/borehole > rainwater > unprotected surface water.
• BIS IS 10500:2012 standards: turbidity ≤1 NTU (acceptable); pH 6.5–8.5; TDS ≤500 mg/L (acceptable); E. coli: zero per 100 mL; residual chlorine ≥0.2 mg/L at tap.
• Treatment sequence: screening → sedimentation → coagulation-flocculation (alum) → filtration → chlorination (break-point chlorination; residual ≥0.2 mg/L).
• Slow sand filtration operates via the Schmutzdecke biological layer; no coagulation needed; 99.99% pathogen removal.
• Waterborne disease categories: bacterial (cholera, typhoid), viral (hepatitis A, hepatitis E), protozoal (amoebiasis, giardiasis), helminthic (guinea worm).
• Cholera toxin locks adenylyl cyclase 'on' via ADP-ribosylation → cAMP↑ → massive secretory diarrhoea; treatment is ORS/IV fluids.
• Hepatitis E is waterborne (faecal-oral), self-limiting in general population but 30% mortality in pregnant women in the third trimester—a clinical emergency.
• Hepatitis B and C are NOT waterborne (blood-borne).
• Guinea worm is near-eradicated—a surveillance and containment success story.
• Rainwater harvesting: rooftop or surface run-off systems; sealed storage; must be chlorinated or boiled before drinking; manage to prevent mosquito breeding.
• Water quality surveillance uses MPN/membrane filtration tests; residual chlorine DPD field testing; Jal Jeevan Mission GP-level laboratories.

REFLECT

Consider a district in India where the Jal Jeevan Mission has just provided piped water to 80% of rural households. The remaining 20% still use open wells. During the post-monsoon season, a cluster of diarrhoeal illness appears. As the district medical officer, how would you decide which households are at risk, and what steps would you take in the first 48 hours of the investigation? Reflect also on the longer-term tension: the infrastructure improvement has reduced but not eliminated risk—how do you address the 20% who remain unprotected, and what community-level water quality monitoring system would you design?