Variations in rainwater quality from roof catchments

摘要: The quality of rainwater from a tile and galvanized-iron type roof catchments were analysed over period 5 months. Examination staggered I litre samples collected during rainfall event showed that the concentration various pollutants high in first but decreased subsequent with few exceptions. Faecal coliform total counts ranged 8–13 (tile roof) 4–8 (iron to 41–75 25–63 colonies per 100 ml, respectively. However, no faecal coliforms detected fourth fifth both roofs. pH open was acidic increased slightly after falling on average zinc concentrations run-off about 5-fold higher compared roof, indicating leaching action well below WHO limits for drinking water quality. Lead remained consistently all exceeded guidelines by factor 3.5. For area studied, “foul flush” volume 51. would be minimum safeguard against microbiological contamination metals content indicate need some form treatment. Rainfall intensity number dry days preceeding significantly affects catchment systems.