Abstract

A study was carried out for purpose of grasping the status of bacteriological contamination of the public wells in Iri city, during the period from 1 to 15 August, 1974. Coliform groups were detected by membrane filter method and physical conditions of the well were checked. 1. The households which used the piped water occupied 70.8 per cent (11,907 households) out of total households Iri city. 2. Temperature of the well water was 38 out of 50 samples (72.0%) with 12.1 to 16.0 degrees C and 9 wells with 10.1 to 12.0 degrees C. 3. The pH values range of the well water was 6.0 to 7.9, 11 cases of 22.0 per cent less than 6.5 and 8 cases of 16.0 per cent more than 7.5. 4. The residual chlorine was found at 15 samples (30.0%) contained 0.1 to 0.5ppm, 9 samples (18.0%), 0.6 to 1.0 ppm after 24 hours of chlorination. 5. Coliform groups were found at 49 out of 50 samples (98.0%) before chlorination when 100ml well waters was tested by membrane filter technique and 15 wells(30.0%) were potable for drinking within 24 hours after chlorination. 6. Coliform groups positive were 23 out of 26 samples (88.5%) with no residual chlorine, 12 out of 16 samples (80.0%) with 0.1 to 0.5ppm and none out of 9 with 0.6 to 1.0ppm.