It is natural to think of water when we talk about the Water Supplies Department (WSD). In Hong Kong, both drinking and flushing water are processed by the WSD before being supplied to consumers. As the treatment and distribution of water consumes energy, the WSD is inevitably the top energy-consuming department in the Government. In light of this, the department spares no effort in saving energy. The use of seawater for flushing is an energy-saving green initiative, which can conserve water and energy as it takes less electricity to supply seawater than fresh water.
The WSD has used seawater for flushing for more than 50 years. There are now 21 seafront pumping stations delivering seawater directly to consumers through the seawater supply network. The seawater supply network serves some 80 per cent of Hong Kong’s population, and helps save 270 million cubic metres of fresh water every year. The Salt Water Supply System for the Northwest New Territories commenced last month, and upon its full operation, the coverage of seawater supply will extend to Tuen Mun East, Yuen Long and Tin Shui Wai. By then, a further 700 000 residents will be able to use seawater for flushing, saving an additional 20 million cubic metres of fresh water each year.
There are some operational details to watch out for in the implementation of seawater for flushing in order to conserve energy, enhance operational efficiency and save WSD’s manpower. For example, before flowing into the pumping stations, seawater is drawn through the suction intake screens to remove debris which may cause damage to water mains and pumps. However, these intake screens are a breeding ground for small marine organisms such as seaweed and shellfish, the growth of which will lead to blockage and restrict the passage of seawater, thus lowering pumping efficiency and increasing energy consumption. Colleagues at the WSD have been working hard to find a solution. Sparked by the observation that it is difficult for grass to grow on lawns that are frequently walked on, they developed the Wave-powered Cleaning System after repeated testing. The system makes use of wave energy and tidal action to drive wired brushes scrubbing up and down on the intake screens round the clock to prevent marine growth.
It is also worth mentioning that during the construction of the aforementioned Salt Water Supply System for the Northwest New Territories, the WSD installed an intelligent pumping control system at Lok On Pai Salt Water Pumping Station. It uses a genetic algorithm - an optimisation method simulating the evolution of living species - to arrive at the best solution more quickly and to find out the best combination of pumps to operate at maximum efficiency. This method saves energy as it turns the pumps on and off automatically based on real-time data, and takes into account the water levels of salt water service reservoirs, tides, power tariff rates and demand for water supply.
Another innovative facility that the WSD has developed is the Inline Hydroelectric Generating System. By utilising the residual pressure of water flowing in the water mains instead of using a battery, the system provides electricity in a convenient and cost-effective way to power the equipment for underground water mains monitoring and water pressure management. It can also increase the frequency of data transmission substantially so as to enhance the monitoring functions of the intelligent water network and the service quality of water supply.
To enhance its energy management performance, the WSD worked on the full implementation of the energy management system in accordance with the International Organization for Standardization (ISO) 50001 early last year and applied for certification to the Standard for the entire WSD, including its Headquarters, a mechanical and electrical workshop, five offices and more than 140 water installations. To achieve the certification, the WSD enhanced its energy policy and targets, compiled a manual on the energy management system and strengthened the mechanism for continuous monitoring, review and performance improvement. It has also provided training for 450 frontline supervisors to promote participation and integration in the energy management culture. After months of hard work, the WSD was awarded the certification late last year and became the first government department in Hong Kong to have received such an honour.
Attention to detail is the key to success. The innovative spirit of our WSD colleagues and their pursuit of continuous improvement are worthy of high praise.
19 April, 2015
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