A Benchmark for Zero Water Use in Commercial Building: Melbourne's 60L
by Doug Pushard

As the trend toward environmental awareness continues in both the private and public sector, more and more zero and low-impact buildings are being designed and built. Most of these projects are focused primarily on electrical energy usage, with water use as an afterthought. This is especially so for commercial buildings - with one noteable exception: the 60L office building in Melbourne, Australia, which was designed with water efficiency as an integral part of the design.

"World-class low-water usage was the goal", said Alistair Mailer, Project Manager for the Green Building Partnership. The building was completed in 2002 and houses 15 tenants and over 200 occupants. "We try very hard to educate our tenants about the 'green' aspects of the building and its environmental credentials. It is surprising how many people, once they enter the building, immediately appreciate many of its 'green' aspects. Our water tanks and water treatment are highly visible on the ground floor of the building - a conscious effort was made to ensure that water was truly an icon issue for the building."

But this is not a typical office building. The building relies almost exclusively on rainwater; including for drinking water.

The rain is collected from the roof, stored in two tanks on the ground floor, filtered, and then sterilized prior to use by tenants in taps and showers. Rainfall from the roof is harvested, then transferred into the holding tanks via a 'Syfonic' system, which uses gravity to create a syphon effect, which means water transfer is faster and pipe diameter can be greatly reduced.

More than 132,000 gallons (500 kiloliters) of rainwater can be collected in an average year. Consequently, the building is almost totally self-sufficient. The only major system not planned to use the rainwater was the fire sprinkler system, which is mandated to be connected to the municipal water system.

Melbourne, Australia is blessed with a good supply of rain - about 25.8 inches (657 mm) annually, and gets 8-10 days of rain most months. The water storage tanks, usually one of the most expensive components of the system, did not have to be super-sized to store water for extended dry periods, which Melbourne sometimes experiences, because water efficiency was planned into the building.

The 60L building includes waterless urinals and low-flow shower heads and toilets, greatly reducing the overall water requirements. The storage tanks are connected to a 4-stage treatment system consisting of 3 filters and a UV sterilization lamp and supply potable water to the showers, sinks, and the kitchen (see the sidebar and related topics for more information on the exact system components).

Used water from the above components is then fed into a combined grey and blackwater biological sewage treatment system. The treated 'reclaim' water is further filtered and UV sterilised for use in toilets, the roof garden, and the water feature. Any excess 'reclaim' water overflows into the city sewer system.

"The objective of the building was to provide an example of a commercially viable, significantly more environmentally sustainable commercial office development, to help bring about a change in the commercial building sector", explains Alistair. "Water was considered an 'icon' issue for the building". Compared to a commercial building of equivalent size, the 60L building consumes about 50% less water due to low-flow toilets, waterless urinals, and low-flow shower heads. These low-use water fixtures also greatly reduce the required tank size, providing a cheaper overall water catchment system and, as importantly, a space savings.

Over the last year, the building achieved an 80% water savings without the reclaimed sewage treatment system working. It is expected that with harvesting rainwater and with the reclaimed water system fully functioning, this integrated system should continually supply upto 95% of the buildings needs depending on rainfall patterns. With larger tanks, an even higher percentage would have been possible, since during prolonged rains, the existing storage tanks occasionally overflow.

Most importantly, this building proves that today, it is almost possible to build zero water-use commercial buildings. It simply requires advanced planning and the desire to build green!

Water rates have been slowly increasing in Melbourne, as the Victoria State Government pursues a dual policy of encouraging conservation and increasing the water prices. As rates continue to increase and builders become more aware of buildings like the 60L, more sustainable office buildings are sure to follow.

Links:

Related Webpage: Schematic of the 60L potable water system (PDF)
Related Resource:Handbook of Water Use and Conservation
Related Article: Zero Runoff Should be the GOAL!
Related Article: Berms and Swales

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