Global water security is a severe issue that threatens human health and well-being. Finding sustainable alternative water resources has become a matter of great urgency. For coastal urban areas, desalinated seawater c...Global water security is a severe issue that threatens human health and well-being. Finding sustainable alternative water resources has become a matter of great urgency. For coastal urban areas, desalinated seawater could serve as a freshwater supply. However, since 20%-30% of the water supply is used for flushing waste from the city, seawater with simple treatment could also partly replace the use of freshwater. In this work, the freshwater saving potential and environmental impacts of the urban water system （water-wastewater closed loop） adopting seawater desalination, seawater for toilet flushing （SWTF）, or reclaimed water for toilet flushing （RWTF） are compared with those of a conventional freshwater system, through a life-cycle assessment and sensitivity analysis. The potential applications of these processes are also assessed. The results support the environmental sustainability of the SWTF approach, but its potential application depends on the coastal distance and effective population density of a city. Developed coastal cities with an effective population density exceeding 3000 persons.km-2 and located less than 30 km from the seashore （for the main pipe supplying seawater to the city） would benefit from applying SWTF, regardless of other impact parameters. By further applying the sulfate reduction, autotrophic denitrification, and nitrification integrated （SANI） process for wastewater treatment, the maximum distance from the seashore can be extended to 60 km. Considering that most modern urbanized cities fulfill these criteria, the next generation of water supply systems could consist of a freshwater supply coupled with a seawater supply for sustainable urban development.展开更多
Within the concept of sustainable construction, with sensible and conscious use of finite natural resources, every effort to save and reuse raw-materials is considered an important step to be adopted in buildings, fro...Within the concept of sustainable construction, with sensible and conscious use of finite natural resources, every effort to save and reuse raw-materials is considered an important step to be adopted in buildings, from project, implantation and construction to operation and maintenance throughout their lifecycle. This study aims at showing the application of a system that reuses condensed water drained from air-conditioner evaporators （which are usually disposed of）, and a plan to use this water for toilet flushing, reducing consumption of treated water bought from water companies. The authors verified that each air-conditioner specified in the project of a commercial building--used as reference here--produces 4.8 L of water per hour of operation. This result in a daily accumulated volume of 4,290 L, which represents a significant part of the amount needed to supply all the toilets in the building. A water capture system located at a strategic intermediate floor would be able to store this water and pump it into a special reservoir on the roof of the building, to be distributed into toilet flush pipes. By applying this technology, the authors seek to considerably reduce the expected treated water consumption and consequently decrease water bill costs.展开更多
文摘Global water security is a severe issue that threatens human health and well-being. Finding sustainable alternative water resources has become a matter of great urgency. For coastal urban areas, desalinated seawater could serve as a freshwater supply. However, since 20%-30% of the water supply is used for flushing waste from the city, seawater with simple treatment could also partly replace the use of freshwater. In this work, the freshwater saving potential and environmental impacts of the urban water system （water-wastewater closed loop） adopting seawater desalination, seawater for toilet flushing （SWTF）, or reclaimed water for toilet flushing （RWTF） are compared with those of a conventional freshwater system, through a life-cycle assessment and sensitivity analysis. The potential applications of these processes are also assessed. The results support the environmental sustainability of the SWTF approach, but its potential application depends on the coastal distance and effective population density of a city. Developed coastal cities with an effective population density exceeding 3000 persons.km-2 and located less than 30 km from the seashore （for the main pipe supplying seawater to the city） would benefit from applying SWTF, regardless of other impact parameters. By further applying the sulfate reduction, autotrophic denitrification, and nitrification integrated （SANI） process for wastewater treatment, the maximum distance from the seashore can be extended to 60 km. Considering that most modern urbanized cities fulfill these criteria, the next generation of water supply systems could consist of a freshwater supply coupled with a seawater supply for sustainable urban development.
文摘Within the concept of sustainable construction, with sensible and conscious use of finite natural resources, every effort to save and reuse raw-materials is considered an important step to be adopted in buildings, from project, implantation and construction to operation and maintenance throughout their lifecycle. This study aims at showing the application of a system that reuses condensed water drained from air-conditioner evaporators （which are usually disposed of）, and a plan to use this water for toilet flushing, reducing consumption of treated water bought from water companies. The authors verified that each air-conditioner specified in the project of a commercial building--used as reference here--produces 4.8 L of water per hour of operation. This result in a daily accumulated volume of 4,290 L, which represents a significant part of the amount needed to supply all the toilets in the building. A water capture system located at a strategic intermediate floor would be able to store this water and pump it into a special reservoir on the roof of the building, to be distributed into toilet flush pipes. By applying this technology, the authors seek to considerably reduce the expected treated water consumption and consequently decrease water bill costs.
