Ana Briga-Sá

Wastewater and greywater reuse on irrigation in centralized and decentralized systems - an integrated approach on water quality, energy consumption and CO2 emissions.

Wastewater and greywater have different scales of end-uses in irrigation in Portugal. Wastewater is treated in a central wastewater treatment plant and reused in public/private large areas of irrigation, like agriculture, public gardens and golf courses. On the contrary, greywater reuse is generally applied in in situ small scales, treated and used in the same place, generally in the production site. The main aim of this paper is to compare the two types of systems: a wastewater centralized reuse system (WWCRS) and a greywater decentralized reuse system (GWDRS) in terms of water quality, energy consumption and CO2 emissions. In this paper, the main characteristics of both streams are presented and the degree of treatment required in each stream is analyzed. The advantages and disadvantages of its reuse in different scales, in terms of water quality, energy consumption and CO2 emissions are discussed. A methodology to calculate the energy consumptions and CO2 emissions related to wastewater treatment that may be applied in different cases is presented. A hypothetical example of the two systems: one referring to a WWCRS and the other to a GWDRS is presented. The energy consumption and the CO2 emissions are analyzed and compared. The WWCRS needs a higher degree of treatment and so it spends more energy and leads to more CO2 emissions to the environment than the GWDRS that consumed between 11.8 and 37.5% of the energy consumed in the WWCRS considering the same number of inhabitants served.

A contribution for the improvement in thermal insulation of tabique walls coated with metal corrugated sheets

Tabique is a traditional Portuguese building technique using timber and earth and was intensively applied until the 20th century. There is an impressive tabique heritage that requires maintenance and rehabilitation interventions. Taking into account the facts that technical and scientific publications related to this particular technique are lacking and that the technique is also applied worldwide, this research work is a very relevant one. This study aims at studying the thermal insulation behaviour of tabique walls and in particular, tabique walls coated using metal corrugated sheets and thermally reinforced with an insulation material. This type of building component is initially characterized and some building details concerning the metal corrugated sheet coating are described. An experimental work was conducted to determine the thermal transmission coefficient of the tabique wall samples. It was concluded that providing the tabique wall coated with metal corrugated sheets with a 3 cm extruded polystyrene board results in a thermal insulation improvement of 61%. These results revealed that the thermal insulation reinforcement of tabique walls is possible and it may be a straightforward building procedure because it can be achieved using the thermal insulation building materials that are currently being used. Therefore, the thermal insulation reinforcement of tabique walls seems feasible. Furthermore, the thermal insulation parameters obtained in this study are similar to the ones obtained for currently applied walls solutions in new buildings. This technical fact may provide guidance for the possibility of using solutions used in old buildings to meet the thermal comfort requirements expected in today’s times. The knowledge gained will also be useful to support future proposals of energy rehabilitation solutions. Practical implications: In this article, tabique construction and its relevance worldwide are discussed. This article highlights the building details concerning the use of metal corrugated sheet coating on tabique walls and evaluates the thermal insulation behaviour of this wall system. The outcomes indicate that it is possible to improve the thermal insulation of a tabique wall. The data obtained in this study may be valuable for repairing tabique walls and may also inspire innovative building solutions in modern industrial practice.

In situ evaluation of water and energy consumptions at the end use level: The influence of flow reducers and temperature in baths

Nowadays, water and energy consumption is intensifying every year in most of the countries. This perpetual increase will not be supportable in the long run, making urgently to manage these resources on a sustainable way. Domestic consumptions of water and electric energy usually are related and its important to study that relation, identifying opportunities for use efficient improvement. In fact, without an understanding of water-energy relations, there are water efficiency measures that may lead to unintentional costs in the energy efficiency field. In order to take full advantage of combined effect between water and energy water management methodologies, it is necessary to collect data to ensure that the efforts are directed through the most effective paths. This paper presents a study based in the characterization, measurement and analysis of water and electricity consumption in a single family house (2months period) in order to find an interdependent relationship between consumptions at the end user level. The study was carried out on about 200 baths, divided in four different scenarios where the influence of two variables was tested: the flow reducer valve and the bath temperature. Data showed that the presence of flow reducer valve decreased electric energy consumption and water consumption, but increased the bath duration. Setting a lower temperature in water-heater, decreased electric consumption, water consumption and bath duration. Analysing the influence of the flow reducer valve and 60°C temperature simultaneously, it was concluded that it had a significant influence on electric energy consumption and on the baths duration but had no influence on water consumption.

Energy consumption, CO2 emissions and costs related to baths water consumption depending on the temperature and the use of flow reducing valves

In the domestic segment, various appliances and processes consume great amount of water and, consequently, energy. In this context, the main aim of this study is to analyse the impact of water temperature, flow and bath duration in water and energy consumptions. The impact on CO2 emissions and a simple costs analysis were also carried out. It included a monitoring plan of 197 baths taken under different scenarios of water temperature and flow. It was concluded that increasing water consumption leads to an increase on energy consumption and that both resources consumptions increase with bath duration. Bath temperature had influence not only on energy consumption, as expected, but also in water consumption, what may be explained by the users satisfaction during baths with higher temperatures. The use of a flow reducing valve is not a guarantee of water saving which can also be related to the users satisfaction patterns, given that the introduction of a flow reducing valve can lead to a bath duration increase. In what concerns to the CO2 emissions, it was concluded, as expected, that higher values are obtained for baths with higher temperatures given their relation with higher energy consumptions patterns. A simple costs analysis revealed that having flow reducing valves, with a bath temperature of 75 °C, increased the costs with electricity and water in 119% and 32%, respectively, when compared with a temperature of 60 °C.

Which are the factors that may explain the differences in water and energy consumptions in urban and rural environments

Rural and urban environments present significant differences between water and energy consumptions. It is important to know, in detail, which factors related to the consumption of these two resources are different in both environments, once that will be those important to manage and discuss in order to improve its use efficiency and sustainability. This research work involves a survey whose aim is to find the factors that in rural and urban environments may justify the differences found in water and energy consumptions. Besides the collection of water and energy consumption data, this survey analyzed 80 variables (socio-demographic, economic, household characterization, among others), that were chosen among the bibliography as possible factors that should influence water and energy consumptions. After the survey application in rural and urban areas and the data statistical treatment, 42 variables remained as truly differentiating factors of rural and urban environments and so as possible determinants of water and energy consumptions. In order to achieve these objectives, a descriptive data analysis and statistical inference (Mann-Whitney-Wilcoxon test and the Chi-square test of homogeneity) were performed. All the 42 differentiating variables that result from this study may be able to justify these differences, however this will not be presented in the paper and it is reserved for future work.