Replumbing of university halts flow of money down the drain

PUBLISHED : Saturday, 21 November, 2009, 12:00am
UPDATED : Saturday, 21 November, 2009, 12:00am

Normally when people finish washing their hands, the water simply goes down the drain.

But at a Hong Kong university it is being collected, treated and used for irrigation by a system that the developers say could be useful in rural areas where water is scarce.

City University of Hong Kong has invested HK$2.6 million on a recycling system that can turn 70 metric tonnes of grey water - from washing and showers but not from toilet flushing - into clean water every day.

The output roughly equals the daily water consumption of 500 people, making the system the largest in the city.

The investment includes the cost of the recycling system developed by the Productivity Council and installation of pipes to separate the grey water from flushing water.

For the past six months, water from wash basins in 60 toilets and condensation from an air conditioner have been collected and recycled.

The recycled water is used to replace tap water for irrigation, the facilities manager of the Kowloon Tong university, Philip Ling Chi-ming, said. 'We used to rely on underground water for irrigation, but there's less of it since the neighbourhood was developed,' he said. Festival Walk is one of the recently developed landmarks in the area.

The cost of operation, including chemicals, electricity and consumables, is HK$1.50 per cubic metre and the university saves about HK$500 a day because it does not have to pay water and sewage charges for 70 tonnes of water.

The Productivity Council did research for two years before the system's installation at the university, the council's principal consultant of environmental management, Dr Anthony Ma Yiu-wa, said.

Like other treatment systems, the process uses micro-organisms to decompose organic matter in the waste water.

But this system uses folded boards in the tank that encourage more rapid multiplication of the tiny bugs.

Ma suggested the system could be useful for venues outside the city centre where water supply is scarce, such as camp sites and resorts.

University campuses, sports grounds and swimming pools, which have more space and a lot of shower facilities, are also possible sites for installation.

Daily savings

The operating cost of the system is about HK$1.50 per cubic metre of water

The saving to the university in not having to pay water and sewage charges on 70 tonnes a day is, in HK dollars: $500