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Universidade de Coimbra (2015)

Utilize este identificador para referenciar este registo

Almeida, Giovana Santos

Titre : Utilize este identificador para referenciar este registo

Development of tools for an efficient water use and reuse

Auteur : Almeida, Giovana Santos

Université de soutenance : Universidade de Coimbra

Grade : Tese de doutoramento em Engenharia Civil 2015

This thesis proposes and analyzes different techniques which aim to provide better and more reliable information about water use and reuse. Initially, this thesis proposes a decision support system (DSS), which identifies the potential level of water reuse considering features that appear to be relative with water shortages. The proposed DSS uses a fuzzy inference system (FIS) for multi-criteria decision making and was designed based on the information from a data-set composed of 155 regions for agriculture and 183 cities for urban environments. In order to identify the suitable factors to compose the FIS, the information provided by data-set was correlated with the water reuse level. It was observed that the environmental factors, such as drought severity and water availability, and structural factors, such as the water exploitation index (WEI), water uses, population density, and waste-water treatment rate, are satisfactorily correlated with agricultural and urban reuse. Given the environmental and structural features, the proposed FIS is very reliable in identifying whether the studied sample has reuse potential or not, with 96\% accuracy in urban reuse and 90\% in agricultural reuse. The potential water reuse analysis indicated that there is less demand for urban water reuse than for agricultural water reuse. In order to improve the urban reuse, this work also proposes techniques to estimate the quality and quantity of a household’s gray water streams. To estimate water use (quantity), a new method was developed that uses flow rate and pressure signals to identify which fixture was in use (e.g. tap, toilet flush, shower, etc.). In order to simulate a bathroom and kitchen, an experimental facility was constructed. The intention of the first phase of experiments was to identify the electronic signatures of each fixture. Five classes for fixtures identification were being monitored : kitchen tap (C1), washbasin tap (C2), Bidet tap (C3), shower (C4) and toilet flush (C5). GDX and SVM were both used to identify the best classifier for the data. The features characteristics were extracted in both the time and the frequency domains and a feature selector was used to select representative features from the signals in order to improve the process of classification. The fusion by majority vote of the SVM classification results in the time domain presented the best accuracies : 92\% for C1, 94\% for C2, 94\% for C3, 100\% for C4 and 100\% for C5. This result indicated that each feature has a specific signature that can be recognized by the classifiers. In the second experimental phase different pipe lengths were used. The results using the SVM classifier indicated that differences in pressure improve the classification accuracies in 4\%.. Signals composition with kitchen tap signals was also analyzed in order to test signal accuracy with two fixtures in use. The results were also good for pressure signals in the time domain : 99\% for kitchen tap and washbasin tap, 97\% for kitchen tap and bidet tap, 99\% for kitchen tap and shower and 100\% for kitchen tap and toilet flush. The future expectation is to complete the identification system with fixtures composition and test the algorithm in a real building. The data provide by the acquisition system developed in this work was also used for head losses and the coefficient of simultaneity studies. The results indicated that the data provided by the experimental facility are suitable for these studies because they are compatible with those presented by manufacturers and literature. To estimate the water quality for reuse, some methods were presented in this work for household stream collection and analysis. The studies presented in this work indicated that the kitchen and laundry streams present a greater concentration of pollutants than the washbasin or the bath. This result is in accordance with many studies in this field. The pollutant charge, the treatment removal rate and the water reuse standards limitation was used to estimate which streams are more suitable for reuse in households. Considering the four houses analyzed, it is estimated that the implementation of the toilet flushing reuse system is feasible and could contribute to save about 15\% of drinking water. Furthermore, the reparation of the leakage presented in two households could save up to 35\% of the volume. These values indicated that significant amounts of water could be saved if water use efficiency and reuse techniques are implemented in buildings.

Mots clés  : Uso da água - Reutilização da água


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