BEAM Plus New Buildings

BEAM P

LUS FOR

UILDINGS

ATER

)

ERSION

1.2

4 W

ATER

ECYCLING

Page 132

ACKGROUND

Recycling of grey water not only helps to reduce the demand for potable

water supply, but also provides a reliable source in case of supply

interruptions. When properly done, it is possible to reuse all wastewater

for various purposes. A grey water recycling system is one which collects

grey water (reclaimed condensate, etc) for treatment and distributes the

treated water to the points of use, such as for irrigation, cleaning, or for

toilet flushing where seawater supply is not available. Another potential

use of the recycled water is for evaporative heat rejection system in air

conditioning, which will provide an energy benefit and improves the cost-

effectiveness of water recycling.

Water quality should meet appropriate criteria, such as that outlined by

ACQWS [1], the Building Research and Information Association [2], or

similar authoritative guidance.

Due consideration has to be given to the amounts of water that can be

generated and how this matches with the amounts that can be put to

use; otherwise there is little incentive to recycle.

The problem for Hong Kong’s high-rise dense built environments is that

the potential for collecting rainwater is limited. Yang et al [3] provide the

main parameters and their relationship to estimate the amount of

rainwater that may be collected on different roof areas and different sizes

of tanks, based on the amount of rainfall as recorded by the Hong Kong

Observatory.

Well-populated buildings not supplied with seawater for flushing would

be a good candidate for water recycling, otherwise reuse is likely to be

limited, depending on the extent of cleaning, irrigation and the types of

equipment used for cooling.

Water Supplies Department. ACQWS Paper No. 14 – Treated Effluent Reuse at Ngong Ping.

BSRIA, Greywater and Rainwater Systems: Recommended UK Requirements, The Building Services Research and

Information Association, Final Report 13034/1, March 1997.

Yang H X, Chow W H, Burnett J. Water and Energy Conservation of Rainwater Collection Systems on Building Roofs.

Advances in Building Technology, Vol. 2. Elsevier. 2002. pp 1281-1288.