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Modelling of a roof runoff harvesting system: The use of rainwater for toilet flushing

Vialle, Claire and Sablayrolles, Caroline and Lovera, Maurin and Huau, Marie-Christine and Vignoles-Montrejaud, Mireille Modelling of a roof runoff harvesting system: The use of rainwater for toilet flushing. (2011) Water Science and Technology: Water Supply. 151-158. ISSN 1606-9749

(Document in English)

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Official URL: https://doi.org/10.2166/ws.2011.031


The water balance of a four-people family rainwater harvesting system was calculated in a case study. The experimental water saving efficiency (WSE) was calculated as 87 %. A simple computer model was implemented to simulate the behaviour of the rainwater harvesting system. In general, the rainwater collector volumes predicted by the daily model had shown a good correlation with the experimental values. The difference between the experimental and the predicted values for the stored volume can be explained by the lack of maintenance of the system that can affect its performance. On the basis of a long-term simulation of 20-year rainfall data, the following parameters were calculated: rainfall, water demand, mains water, rainwater used, over-flow and WSE. The collection of rainwater from roofs, its storage and subsequent use for toilet flushing can save 42 m3 of potable water per year for the studied system. The model was also used to find the optimal size of the tank for the single-family household: a storage capacity of approximately 5 m3 was found to be appropriate. The storage capacity and tank size were distinguished. The importance to take into account the dead volume of the tank for the sizing was indeed highlighted.

Item Type:Article
Additional Information:©IWA Publishing 2011. The definitive peer-reviewed and edited version of this article is available at www.iwapublishing.com
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
French research institutions > Institut National de la Recherche Agronomique - INRA (FRANCE)
Other partners > Veolia Environnement (FRANCE)
Laboratory name:
Deposited On:27 Jan 2012 13:50

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