Pathogenic pollution in drinking water

Pathogenic pollution of drinking water is the contamination of water by disease-causing micro-organisms (pathogens) – bacteria, viruses, protozoa and helminth (worm) eggs – that come mainly from human and animal faeces. It is the most dangerous form of water pollution in developing countries because even a small dose can cause disease and outbreaks.

Main pathogens and diseases

Indicator organism: since pathogens are hard to test, water is tested for faecal coliform / E. coli. Nepal's National Drinking Water Quality Standards require 0 E. coli per 100 mL.

Sources: open defecation near sources, leaking septic tanks and sewers, cross-connection of sewer and water pipes, uncovered wells and springs, animal waste, unsafe storage at home, flood water.

Transmission route (fecal-oral route)

             +--> Fluids (water) ------+
             +--> Fingers -------------+
 FAECES -----+--> Flies ---------------+--> FOOD --> MOUTH
             +--> Fields/soil ---------+       (new host)

1. Fluids – drinking contaminated water directly (water-borne).
2. Fingers – unwashed hands touch food or mouth (water-washed diseases, due to lack of water for hygiene).
3. Flies – carry faecal matter to food.
4. Fields – contaminated soil and vegetables.
5. Food – prepared with contaminated water or hands.

Prevention measures

At source and in the system

1. Safe excreta disposal – toilets for all, no open defecation; latrines at least about 15 m from and downhill of water sources.
2. Protect intakes, springs and wells (fencing, sealed covers, sanitary seal).
3. Treatment: sedimentation, filtration (slow sand filter) and disinfection by chlorination with residual chlorine in the supply.
4. Maintain pipelines; avoid intermittent supply and cross-connection with sewers.
5. Regular water quality testing for E. coli.

At household level 6. Boiling, ceramic or biosand filters, chlorination (e.g. Piyush), SODIS (solar disinfection). 7. Safe storage in covered, narrow-mouthed vessels; use a ladle, not hands.

Hygiene and health 8. Hand washing with soap at critical times. 9. Food hygiene and fly control. 10. Health education, vaccination (typhoid, polio, rotavirus, hepatitis A) and ORS/zinc for diarrhoea.