Use of Reclaimed Water
Safe and useable water extracted from sewage in the treatment process is becoming increasingly important around the world. Here you can learn exactly what reclaimed water is and how it is being used in Hong Kong.
What is Reclaimed Water?
Most sewage is treated to a certain standard before discharging into receiving water body – usually a river or the sea. In contrast, reclaimed water is more highly treated to make it clear in appearance, odourless and safe for reuse, and it forms part of the water supply. But there is no plan for replacing drinking water by reclaimed water. Rather, it is used in other areas to reduce the overall demand for fresh water.
Why Do We Need Reclaimed Water?
Apart from conserving our drinking water, reclaimed water reduces the amount of treated effluent that is discharged into the aquatic environment. This is beneficial to Hong Kong's highly developed fisheries and seafood industry. And in line with experience around the world, reclaimed water could be used here in the following ways.
- Cleaning roads and vehicles
- Irrigating parks and sport fields
- Flushing toilets
- Fire fighting
- Industrial production
- Urban development and landscaping
With these applications in mind, the Government has developed pilot schemes to explore the possible uses of reclaimed water in Hong Kong.
Use of Reclaimed Water in Hong Kong
At present, the “Reclaimed Water” schemes launched at Ngong Ping Sewage Treatment Works and Sha Tin Sewage Treatment Works are the largest among other sewage treatment works, to promote the use of reclaimed water.
The first scheme at Ngong Ping was commissioned in 2006 when the Ngong Ping Sewage Treatment Works opened on Lantau Island. As the first tertiary treatment works in Hong Kong to produce reclaimed water, Ngong Ping Sewage Treatment Works uses a sequencing batch reactor, dual media filter and disinfection process to reduce organic pollutants, suspended solids, nutrients and pathogenic organisms from sewage to a very low level. The reclaimed water produced is odourless and safe. It is currently used for toilet flushing in nearby public toilets and the Ngong Ping Cable Car Terminal, and also for rearing aquarium fishes and controlled irrigation within the sewage treatment works.
The water reclamation facilities at Sha Tin Sewage Treatment Works, which were commissioned in early 2011, comprise three filtration parts, namely disc filters, ultra-filtration membranes and reverse osmosis membranes. The facility is capable of generating 1,000 m3 of reclaimed water every day for plant cleaning, garden irrigation, toilet flushing and chemicals dilution.
Including Ngong Ping Sewage Treatment Works and Sha Tin Sewage Treatment Works, there are 4 sewage treatment works equipped with water reclamation facilities in Hong Kong. It is expected that valuable information will be collected on how reclaimed water can be used in other parts of Hong Kong.
