Influence of Catchment Surface Material on Quality of Harvested Rainwater

Abstract

Rainwater harvesting (RWH) systems offer an opportunity to diversify the water matrix under drought scenario. However, there is not a robust institutional framework for managing this new source of water. The objective of this study was to evaluate the influence of the catchment surface material on the quality of rainwater collected. Three systems were installed in south-central Chile, which collected rainwater from three different surfaces: gravel tile, zinc-polycarbonate sheets, and clay tiles. The RWH system consists of a first flush diverter and then a storage system with chlorination. The rainwater was characterized by its physicochemical and microbiological properties for its possible final use, considering the current regulations for drinking water and agricultural irrigation. The results indicate that the raw rainwater harvested from different surfaces presented a high mean conductivity of 232 ± 146 µS/cm. Meanwhile, fecal coliform values were <1 MPN/100 mL, which indicates good microbiological quality. Regarding the quality for use as drinking water, it was found that of 39 parameters evaluated according to a reference standard, only the pH was above the indicated limit. Meanwhile, the harvested water presents satisfactory quality for irrigation, except for its sodium (35–50% above the standard) and pesticide values (with respect to 0.028 µg Delta-BHC/L at Site 2).