Evaluating the effect of roof type variations on the quality of rainwater runoff for rainwater harvesting development

Rainwater harvesting is the local collection of rainwater and its storage using various technologies, with the aim of using it to meet water needs in human activities. The factors that affect the quality of rainwater runoff in the rainwater harvesting system are the rainwater harvesting components and external factors, such as climatological conditions that include the intensity of rainfall and dry days. This study aims to analyze the quality of rainwater runoff from various types of roof, the influencing factors, and the potential utilization of rainwater runoff in residential–industrial areas. Three types of full-scale roofs—asbestos, clay tile, and galvanized zinc—were observed. Rainwater runoff was sampled from each type of roof using a composite method. The Mann–Whitney test and Spearman's correlation coefficient were used to determine the significance of the factors that influenced the quality of the rainwater runoff and the relationships of each factor to the quality of rainwater runoff, respectively. The results revealed that internal factors, such as type of roofing material and slope of the roof, have a significant influence on the quality of rainwater runoff, while a high intensity of rainfall and long dry periods, as external factors, caused higher concentrations of contaminants in rainwater runoff. Though some parameters of rainwater runoff met quality standards, it is recommended that a simple water treatment unit be installed to ensure clean water for sanitation needs.