CPGreen - Green Design

A striking example of a development that maximizes water supply is the new Singapore Racecourse.

With its extensive irrigation and washing needs, a racecourse can consume vast amounts of water that can result in high operational costs.

Singapore Racecourse

Two strategies were devised:

—	First, waste water discharge from a neighbourhood sewerage treatment plant is captured and treated to standards for non-potable use. This treated water is then used to irrigate the tracks, the paddocks and all landscaped areas of the complex. An automated sprinkler system distributes the water to the tracks.
—	Second, all rainwater landing on the complex is channelled via drains into two reservoirs located at the infield. This water is then pumped into a water storage tower for the washing of stables. The full capacity of the rainwater ponds is 18,000 m³, enough to last a week without rain.

It is estimated that the water systems put in place save some S$900,000 a year.

Other Singapore buildings, designed by CPG Consultants that deploy rainwater collection systems or waste water recycling systems include Changi Airport, The Esplanade — Theatres on the Bay, Tuas Checkpoint and Woodlands Checkpoint.

The Esplanade — Theatres on the Bay

Changi Airport

Tuas Checkpoint

Woodlands Checkpoint

Water is the least discussed environmental issue in building design despite its high profile in national and global discourses. This may be because water efficiency and conservation strategies consist largely of practical measures and technologies that have little impact on the appearance or layout of a building (barring the occasional gesture to rainwater collection). Of the decisions made during concept design, landscaping and external glazing have the most significant impact on water use. Beyond that
a water-savvy development looks inwards to the efficiency of its fittings and choice of reticulation systems. There are two options here: reduce demand and maximize supply.

Demand depends very much on building type. Residential demand is driven by occupant activities such as bathing and washing. Commercial buildings, such as office towers, can use as much as 50% of their water in cooling systems. The first course of action is establishing the efficiency of equipment in the market. There are, for instance, many choices for bathroom and toilet fittings from low capacity cisterns to waterless urinals.

The second involves determining the quality of
water needed. Not all activities require a potable supply, which is water fit for human consumption. Increasingly designers look to alternatives sources to maximize supply such as rainwater collection, grey and black water recycling. Rainwater collection systems can potentially yield potable water, dependent on site area and run-off surface. Grey and black water systems yield a lower grade of non-potable water. A decision on which technology to buy into begins by matching what is needed, in terms of quantity and quality, with what is available, in terms of runoffs and discharge (see text below).

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This is the most effective and economical strategy. The most obvious strategy is use of water-conserving fixtures and fittings. Few designers are aware of the differences between fittings and their potential impact on water use. Here are a few examples:

Toilets
Toilets account for a significant portion of total
water demand. An inefficient cistern can use up to 10 litres/flush. A dual flush toilet can reduce water demand to an average of 4 litres/flush. There are different types of water-efficient toilets on the market, ranging from low and ultra-low flush toilets
to composting toilets that use no water at all.

Urinals
While a standard urinal uses an average of
6 litres/flush, water-efficient urinals use 2.8 litres/flush. A range of waterless urinals is now available. These use an oil barrier between the
urine and the atmosphere, preventing odours
from escaping.

Taps
Reducing the flow rate of taps significantly reduces water use. A tap can release as much as 10 to
12 litres/minute, which can be reduced to 2.5 litres/ minute with the installation of thimbles and flow regulators. Self-closing taps and infrared devices (that detect presence of user) reduce waste by limiting the duration of flow. Some of these devices, however, require energy to operate and are more expensive. A combination of regulators and self-closing taps can achieve very significant savings.

Showers
Showers are one of the biggest consumers of water in the home. A standard showerhead can have a flow rate of up to 11 litres/minute in use. Efficient showerheads have flow rates of 7 to 9 litres/minute while highly efficient showerheads ones operate
at 5 litres/minute or less. Showers can be fitted
with meters that show the amount of water being consumed and the duration of the shower. This
will encourage users to better manage their consumption.

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Rainwater can be harvested from the impervious surfaces such as rooftops and other paved surfaces. The quality of the rainwater from rooftops is higher than from any other paved surfaces, requiring less treatment when compared with water collected from surfaces exposed to people and vehicular traffic.

Grey water is collected from indoor sources other than toilets such as showers and hand basins. It requires treatment such as filtration and disinfection. Condensate discharge from air conditioning systems can be included in this category, although this is likely to be of a higher quality than other grey water sources.

Black water is the discharge from the toilet and contains significant nutrient concentrations. This means that it needs to be treated to a very high level, especially with respect to disinfection.

The best-designed system matches the quantity of the supply from source with demand of the end-use at the lowest possible cost of treatment. Matching source to end use should factor the minimum level
of treatment required. Rainwater can be a potable source depending on where and how it is collected. For a site where rainwater might be contaminated by air pollution, its deployment is best restricted to non-potable uses such as flushing and irrigation.

Treated grey water can be used for flushing as
well. Other uses include irrigation and cooling tower make-up. Treated black water is most suited for
sub-surface irrigation of landscape.

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Reducing Demand

Maximising Supply

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