Civil Engineering Reference
In-Depth Information
• Eliminate leaks;
• Specify water-eficient labelled products;
• Recover non-sewage, roof water, groundwater and grey water for on-site activi-
ties use.
2.2.4.2 Storm Water and Wastewater Reuse
In urban areas storm water is generated by rain run-off from roof, roads, drive-
ways, footpaths and other impervious or hard surfaces. Rainwater can be used for
toilet flushing, laundries or for watering the garden.
Wastewater (grey water
+
black water) re-use decreases effluent volumes,
reducing the stress on existing centralized wastewater disposal systems, which will
work better and last longer.
At an urban scale, waste water treatment plants require an area of 0.5-2 m
2
per
inhabitant. A drop in water consumption in conjunction with the smaller house-
hold sizes plus the increase in the living space requirements per person have
resulted in reduced waste-water flows. The cost of waste-water treatment in large-
scale plants is much greater than the cost of treating drinking water. The energy
requirements of waste-water plants (due to aeration, circulation and transportation
of the waste-water) are also very high. Thus, decentralised waster-water treatment
offers a cost-effective alternative.
Technologies for controlling water consumption are only one aspect of maxi-
mizing water effectiveness; others are wise management of water sources and even
the potential to produce usable water, through treatment technologies or desali-
nation. It is naturally prudent to consider the whole impact of a process such as
desalination due to the intensive energy demands.
Innovative solutions isolate usable partial flows from the water by means of
materials-flow analysis. It is possible, for example, to use rain water in the build-
ing services, e.g. for cooling, with both low-tech solutions for open bodies of
water and even high-tech solution for air conditioning systems already available.
Example: Bank of America Tower, New York (USA)
The Bank of America
Tower is the second-highest skyscraper in New York and the first office tower in
the US to be nominated for LEED Platinum, the highest ecological rating of the
American Green Building Council (Fig.
2.7
). The concept of sustainability also
includes minimizing water consumption partly through the use of rainwater.
The majority of wastewater generated in the building is recycled by collect-
ing sink wastewater, coil condensate from the air-conditioning systems, and roof
storm water into a series of tanks.
Planting to the flat roof of the podium serves to retain rainwater and prevent exces-
sive heat gains. Rain that falls on the surfaces at the top of the tower is fed into four
grey-water tanks at various levels of the building. In the main tank in the basement,
water from various sources is collected and used for cooling purposes and for flush-
ing toilets. The installation of waterless urinals brought the greatest overall saving.
