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-Water reuse networks have been emerging globally for the last 50 years. This article reviews the economic, social and environmental issues related to implementing water reuse networks in cities. This is reflecting the fact that globally many cities are categorised as water scarce areas, where there is growing imbalance between water demand and availability. In this sense, there is a need for sustainable water supply solutions in the imminent future to provide and maintain service reliability, particularly in the face of climate change. To demonstrate the sustainability implications of water reuse practices, we review a case study in London, UK.

Retrofitting existing buildings with appropriate green technologies is an important element of strategies to mitigate climate change. The selection of green technologies can be a challenging task, where multiple criteria exist and interrelate. However, it is still common for decisions to be based on a single criterion, such as energy efficiency or cost. This paper aims to evaluate the application of Multi-Criteria Decision Making (MCDM) methods to the selection of green technologies for retrofitting to existing buildings. The paper begins with a review of MCDM methods and the use of these techniques for selecting technologies to retrofit existing buildings. The applicability of Analytical Hierarchy Process (AHP), a widely used MCDM method, is demonstrated through a case study of a building that is part of a university estate. The findings show that AHP can help to formulate the problem, and facilitate the assessment and ranking of retrofitting measures when multiple criteria are jointly considered. We have shown that by considering environmental and economic criteria, control technologies such as variable speed drives in air handling units, rank most highly in this case. It has also been suggested that social criteria, such as occupant satisfaction, should also be considered as part of the sustainability agenda, although this can be more difficult to achieve than consideration of environmental and economic criteria, which are more readily characterised using quantitative data. We conclude by proposing an integrated green technology assessment and selection framework, which is applicable to existing buildings.

During the normalized phase of COVID-19, droplets or aerosol particles produced by infected personnel are considered as the potential source of infection with uncertain exposure risk. As such, in densely populated open spaces, it is necessary to adopt strategies to mitigate the risk of infection disease transmission while providing sufficient ventilation air. An example of such strategies is use of physical barriers. In this study, the impact of barrier heights on the spread of aerosol particles is investigated in an open office environment with the well-designed ventilation mode and supply air rate. The risk of infection disease transmission is evaluated using simulation of particle concentration in different locations and subject to a number of source scenarios. It was found that a barrier height of at least 60cm above the desk surface is needed to effectively prevent the transmission of viruses. For workstations within 4m from the outlet, a 70cm height is considered, and with a proper ventilation mode, it is shown that the barriers can reduce the risk of infection by 72%. However, for the workstations further away from the outlet (beyond 4m), the effect of physical barrier cannot be that significant. In summary, this study provides a theoretical analysis for implementing physical barriers, as a low-cost mitigation strategy, subject to various height scenarios and investigation of their effectiveness in reducing the infection transmission probability.

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