Quantitative and qualitative evaluation of the use of walls as a new perspective of rainwater harvesting

ABSTRACT The pollution of water supply sources and the need to seek water, which is increasingly distant, adds to the treated water a high monetary value, so the capture and use of rainwater represents a way to reduce costs. In large urban centers, the formation of heat islands takes place, which favors the occurrence of convective rains with winds. Furthermore, the buildings were verticalized, resulting in a larger lateral area compared to that of the roof, making the rainwater-harvesting in walls a promising alternative. The aim of this work was to verify the quantity and quality of the water collected on a glass wall and another concrete wall in the city of Ilha Solteira, São Paulo, Brazil. The average rainfall incidence was of 48.7% in the glass wall and of 33.3% in the concrete wall, with each screen having an average pickup efficiency of 16.21 and 8.27%, respectively. The parameters of water quality (pH, turbidity, electrical conductivity and alkalinity) presented a decrease with the passing of millimeters drained. Water from the glass wall requires no volume of waste according to NBR 15.527/07. No relation was found between rainfall intensity and water quality, as well as catchment efficiency. However, when rainfall occurred on consecutive days, the water quality was higher when compared to its occurrence in dry periods.摘要 水源污染与取水距离不断增加的现状，使得处理后自来水的经济成本居高不下，因此雨水收集与利用成为降低供水成本的可行途径。大型城市中心易形成热岛效应，进而催生伴随强风的对流降雨。此外，城市建筑向垂直化方向发展，使得建筑侧向集水面积远超屋顶面积，因此墙面雨水收集成为极具潜力的替代集水方案。本研究以巴西圣保罗州伊尔索尔特雷拉市为研究区域，旨在测定玻璃墙面与混凝土墙面收集的雨水的水量与水质特征。玻璃墙面的平均降雨捕获率为48.7%，混凝土墙面为33.3%；两类集水面的平均集水效率分别为16.21%与8.27%。水质参数（pH值、浊度、电导率与碱度）随累积降雨毫米数的增加呈下降趋势。根据巴西国家标准NBR 15.527/07，玻璃墙面收集的雨水无需进行初期弃流处理。研究未发现降雨强度与水质、集水效率之间存在显著相关性。然而，相较于干旱间歇期后的单次降雨，连续降雨事件收集的雨水水质更佳。