Rainwater is one of the most promising alternative water sources. However, the financial outcomes of the rainwater harvesting systems are not always assured due to the economic performance of RWH system varies greatly under different climatic conditions.This paper investigates reliability,water saving and benefit cost ratio of RWH system with different storage tanks and under three distinct climatic conditions (i.e.,wet, average and dry year) at four cities in China. It is found that for a standard building (1,600 m2 roof having 560 people), the rainwater supply reliability varies significantly (3.85–20.55%) across four cities. It is found that Guangzhou (South China) is always achieving the highest reliability, greatest annual water saving and highest benefit cost ratio under three distinct climate conditions. In the contrary, Beijing (North-China) is mostly ranked as having the lowest one. These findings are well in line with the historical annual precipitation in these regions. Also, it is found that across these four regions, it is not possible for a RWH system to achieve benefit cost ratio higher than 1.0. These findings indicate that the RWH systems in most regions of China is currently economically unfeasible without government subsidies.
Gravity-driven rainwater harvesting (RWH) system showcases a promising alternative solution to reduce energy consumption in rainwater recycling. However, the economic efficiency is one of the most concerns with regard to the adoption of this green infrastructure. In this study, a commercial official building has a rooftop area of 1600 m 2 and with 560 inhabitants was assumed to apply two configurations of RWH
Rainwater harvesting has become an important strategy to achieve the goal of sustainable development in urban areas. The latest emerged gravity driven micro-filtration technology can effectively reduce turbidity and bacteria to a very low level but still have disadvantages of low removal of dissolved organic substances and low permeate flux. An innovative gravity driven micro-filtration technique using ceramic flat sheet membrane as filter module was established and introduced to the treatment of rainwater that was harvested from a typical official building in GuangZhou, South China. The performance of this process has been evaluated in terms of pollutants (e.g. pH, turbidity, total dissolved solids (TDS), CODcr, NH3-N, DOC,UV254, total Coliforms and E.coli) removal efficiency, and the permeate flux profiles. Results shows that the removal rates of turbidity, TDS, CODcr, NH3-N, DOC,UV254, Coliforms and E.coli were 92.2%, 91.9%, 65.5%, 42.6%, 76.9%, 61%, 96.9% and 95.5%, respectively. The GDM system can run continuously for 60 days without back washing, and the permeate flux stabilized at 22~45 L/(m<sup>2</sup>·h) under a constant water head of 20 kPa. Experimental results demonstrated that the GDM system employing a ceramic flat membrane can significantly improve the organics removal in rainwater.
The application of the RWH system in universities not only helps to reduce financial expenditure but also provides a good opportunity to educate students about sustainable water management. This study uses daily rainfall data of three different climate regimes (dry, average, and wet years) to evaluate the potable water saving and economic efficiency of the proposed RWH system in a university campus in Guangzhou, China. The economic analysis shows that, except for two residential buildings, the installation of the RWH system in the four educational buildings is generally economically viable, with benefit-cost ratios ranging from nearly 1.0 to 2.01 and positive net present values of 5245 to 74963 CNY under normal and wet years. It is also observed that the RWH system in the academic buildings is more economically feasible than the student apartments, and the multi-story apartment building is more attractive in terms of financial returns than the high-rise building. The performance of the data for different buildings helps us to understand the range of water-saving efficiency and economic feasibility of the RWH system, and information on which type of building is appropriate to install an RWH system, which will be of great benefit to sustainable campus construction.
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