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5th International Conference on Rain Water Cistern Systems
"Rainwater Catchment for Future Generations"
Keelung, Taiwan, R.O.C. - August 1991

Section 2: Catchment Water Quality Regulation

Page 52

Rainwater Quality: Pathogens And Heavy Metals

Wanpen Wirojanagud
Khon Kaen University, Thailand


The quality of rainwater samples collected from collecting system (roof and gutter), storage containers (both outdoor and indoor) were evaluated both bacteriologically, using indicator organisms and pathogen isolation, and chemically by analysing heavy metal concentrations. The source of bacteriological contamination was investigated employing the ratio of fecal coliform to fecal streptococci (FC:FS). Information on saitary practices was also investigated.

Approximately 60-91 %, 34-78 %, 43-78 %, and 10-33 % of samples collected from collecting system and storage containers did not meet the drinking water quality standard expressed in terms of total bacterial count, total coliform, fecal colliform, and E.Coli, respectively. About 79-84 % of samples collected from roof and gutter had FC:FS ratios of less than 1, indicating the source of contamination was animal. While about 39 % and 47 % of samples collected from in-house containers had FC:FS ratios of less than 1 and greater than 4 respectively, which indicated the contaminating sources were both animal and human.°The contamination induced by human was mainly caused by unsanitary practices on water handling and usage of the villagers.

Pathogenic contamination was found approximately 1.1 % of samples collected,from such sampling points. The pathogens identified were Salmonella gr.E. and gr.C, V. parahaemolyticus, and Aromonas. The heavy metals analysed in this study included Cd, Cr, Pb Cu, Fe, Mn and Zn. Most of the heavy metal concentrations taken from various sampling points compared favorably with WHO drinking water standards with two exceptions, Mn and Zn. However, Mn and Zn are considered to affect the asdthetic quality of drinking water only and were therefore not significant to health.

The findings from this study indicate that any health risk evolving from the consumption of stored rainwater would be due to bacteriological contamination rather than heavy metal contamination.

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