Department of Engineering, Trás-os-Montes and Alto Douro University (UTAD), Ap. 1013, 5001-801 Vila Real, Portugal; Centre for the Research and Technology of Agro-Environmental and Biological Sciences, UTAD, Portugal.
Department of Engineering, Trás-os-Montes and Alto Douro University (UTAD), Ap. 1013, 5001-801 Vila Real, Portugal.
Sci Total Environ. 2015 Oct 1;529:91-100. doi: 10.1016/j.scitotenv.2015.05.061. Epub 2015 May 22.
A rainwater harvesting system (RHS) was designed for a waste treatment facility located near the town of Mirandela (northern Portugal), to be used in the washing of vehicles and other equipment, the cleaning of outside concrete or asphalt floors, and the watering of green areas. Water tank volumes representing 100% efficiency (Vr) were calculated by the Ripple method with different results depending on two consumption scenarios adopted for irrigation. The RHS design was based on a precipitation record spanning a rather long period (3 decades). The calculated storage capacities fulfilled the water demand even when prolonged droughts occurred during that timeframe. However, because the drought events have been rather scarce the Vr values were considered oversized and replaced by optimal volumes. Notwithstanding the new volumes were solely half of the original Vr values, the projected RHS efficiency remained very high (around 90%) while the probability of system failure (efficiency<100%) stayed very low (in the order of 5%). In both scenarios, the economic savings related to the optimization of Vr were noteworthy, while the investment's return periods decreased substantially from the original to the optimized solutions. A high efficiency with a low storage capacity is typical of low demanding applications of rainwater harvesting, where water availability (Vw) largely exceeds water demand (Cw), that is to say where demand fractions (Cw/Vw) are very low. Based on the results of a literature review covering an ample geographic distribution and describing a very large number of demand fraction scenarios, a Cw/Vw=0.8 was defined as the threshold to generally distinguish the low from the high demanding RHS applications.
雨水收集系统 (RHS) 专为位于米蘭德拉镇（葡萄牙北部）附近的废物处理设施设计，用于车辆和其他设备的清洗、外部混凝土或沥青地板的清洁以及绿地的灌溉。采用两种不同的灌溉用水方案，利用波纹法计算出了 100%效率的水箱容积 (Vr)。RHS 的设计基于一个跨越较长时期（30 年）的降水记录。计算出的储水能力即使在该时间段发生长时间干旱时也能满足用水需求。然而，由于干旱事件相当稀少，因此认为 Vr 值过大，并将其替换为优化后的容积。尽管新的容积仅为原始 Vr 值的一半，但预测的 RHS 效率仍然非常高（约 90%），而系统故障的概率（效率<100%）仍然非常低（约 5%）。在这两种情况下，与优化 Vr 相关的经济节省都非常显著，而投资回报期从原始解决方案到优化解决方案都大幅缩短。对于雨水收集的低需求应用，高效率和低存储容量是典型的，因为可用水量 (Vw) 大大超过了用水需求 (Cw)，也就是说，需求分数 (Cw/Vw) 非常低。基于涵盖广泛地理分布并描述大量需求分数场景的文献综述结果，定义 Cw/Vw=0.8 作为一般区分低需求和高需求 RHS 应用的阈值。
