Water Quality, Contamination and Public Health
This domain tests drinking-water quality, contamination routes and health outcomes. Questions link laboratory parameters to source protection, treatment and public-health response.
Core rules
- Safety is microbiological first: faecal contamination causes diarrhoea, typhoid and hepatitis A. Turbidity can hide pathogens and reduce disinfection efficiency.
- Chemical contaminants include fluoride, nitrate and salinity. Fluoride above permissible limits can cause dental and skeletal fluorosis; nitrate above 45 mg/L as NO3 can cause methaemoglobinaemia in infants. Some Vidarbha and Marathwada groundwater tracts have fluoride and salinity problems.
- Protect the source: wellhead sanitation, septic-tank setback, safe collection and chlorination. Test routinely, not only when water looks dirty.
Worked example
A village well tests nitrate at 60 mg/L as NO3, above the 45 mg/L limit. The handpump is near cattle sheds and a soak pit. Reasoning: blending is unreliable. The response is to stop using the well for infant feeding, provide an alternate safe source, fence and upgrade the sanitation, and retest. Boiling does not remove nitrate; it concentrates it.
Traps
- Judging safety by colour, taste or turbidity alone.
- Boiling to fix chemical contamination.
- Testing one sample and declaring the source safe forever.
- Ignoring sanitation around the wellhead.