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 水源污染以及取水距离日益增加的现状，使得处理后自来水的成本大幅攀升，因此雨水收集与利用成为降低供水成本的可行途径。在大型城市中心区域，热岛效应（heat islands）的形成会催生伴随强风的对流降雨。此外，城市建筑日趋高层化，建筑侧面积相较于屋顶面积更大，使得墙面雨水收集成为颇具潜力的替代方案。本研究以巴西圣保罗州伊利亚索尔泰拉市为研究区域，旨在探究玻璃幕墙与混凝土墙面收集的雨水的水量与水质特征。玻璃幕墙与混凝土墙面的平均降雨收集率分别为48.7%与33.3%，二者的平均集水效率（pickup efficiency）分别为16.21%与8.27%。随着累计降雨深度的增加，雨水的水质指标（pH值、浊度（turbidity）、电导率（electrical conductivity）与碱度（alkalinity））均呈下降趋势。依据巴西国家标准NBR 15.527/07，玻璃幕墙收集的雨水无需进行弃流处理即可达标回用。研究未发现降雨强度与雨水水质及集水效率之间存在显著关联。但在连续降雨事件中，收集的雨水水质相较于旱期降雨后的水质更佳。