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Drinking Water Quality

Hong Kong's raw water (including Dongjiang (DJ) water and rainfall collected from local gathering grounds)  undergoes rigorous treatment processes including coagulation, sedimentation, filtration and disinfection to ensure that the quality of drinking water provided to customers complies fully with the Hong Kong Drinking Water Standards, currently being the corresponding guideline values or provisional guideline values in the fourth edition of the World Health Organization’s Guidelines for Drinking-water Quality published in 2011 (WHO Guidelines).

Drinking water quality, however, can be affected by the condition of a building’s inside service. To safeguard tap water quality, property owners and building managers are advised to carry out proper maintenance of inside service and regular cleaning of water storage tanks.

Water Sampling

Hong Kong Drinking Water Standards

The WHO Guidelines are prepared and updated through the participation of numerous authoritative institutions and hundreds of experts from a wide range of developed and developing countries, and represent the consensus opinion based on worldwide scientific and medical studies. The WHO Guidelines are authoritative, scientific and evidence-based and many developed countries worldwide make reference to them to monitor and control the quality of drinking water.

For years, the Hong Kong Government has been providing drinking water that fully complies with the WHO Guidelines. The Government launched the Action Plan for Enhancing Drinking Water Safety in Hong Kong (Action Plan) in September 2017 to further safeguard the drinking water quality in Hong Kong through a multi-pronged approach.  Under the Action Plan, the Government has engaged an expert consultant to review the approaches, rationales and practices of two international organisations (i.e. the WHO and the European Union) and seven overseas countries (i.e. the United Kingdom, the United States of America, Canada, Australia, Singapore, New Zealand and Japan) in establishing their drinking water standards.  The expert consultant has already completed the review on the 12 metal parameters in the WHO Guidelines. Having taken into account the expert consultant’s findings and consulted the International Expert Panel on Drinking Water Safety appointed by the Development Bureau, the Government adopts the WHO’s guideline values (“GVs”)/provisional guideline values (“PGVs”) as HKDWS for these metal parameters. Further, the expert consultant will also review the remaining WHO’s parameters. Pending the completion of the review, the Government adopts the corresponding WHO’s GVs/PGVs as HKDWS for these remaining parameters.  In addition, the Government, according to the WHO Guidelines, is collecting local water quality data for reviewing the drinking water standards with a view to assessing the appropriateness for some parameters to adopt a standard beyond WHO Guidelines (“WHO+”).  The Government will review the need to include other parameters in the drinking water sampling test at the consumers’ taps as and when appropriate.

In addition, the Water Supplies Department (WSD) also monitors a number of additional water quality parameters with a view to providing information on the general quality of drinking water leaving water treatment works and its long term trend.

Parameters Reasons/Criteria
HKDWS parameters (92) Metals (12 parameters) Considered by WHO to have public health significance in drinking water
Pesticides (33 parameters)
Disinfectants (3 parameters)
Disinfection by-products (14 parameters)
Other Inorganic chemicals (3 parameters)
Other Organic chemicals (24 parameters)
Microbiological (1 parameter) Indicator of bacteriological contamination
Radiological (2 parameters) Screening parameters for radioactivity level in drinking water
Additional parameters (19) Physical (4 parameters) Indicators of general aesthetic, physical, chemical and microbiological quality
Metals (5 parameters)
Other Inorganic chemicals (7 parameters)
Microbiological (3 parameters)

Please visit Hong Kong Drinking Water Standards web page for more details.

Water Quality Monitoring

The WSD has developed a comprehensive and extensive water quality monitoring regime through a series of physical, chemical, bacteriological, biological and radiological examinations covering the HKDWS and the additional parameters for water quality surveillance and operational monitoring.

Water quality throughout the entire water treatment, supply and distribution system is systematically monitored by means of physical, chemical, bacteriological, biological and radiological examinations of water samples taken at catchment, intakes, receiving point of DJ water at Muk Wu Pumping Station, impounding reservoirs, water treatment works, service reservoirs, water distribution systems and consumers’ taps. More than 160,000 samples are taken and tested each year.

The WSD laboratories have been equipped with advanced analytical instruments for trace analysis of various contaminants.

Inductively Coupled Plasma Mass Spectrometer (ICP-MS)
Inductively Coupled Plasma Mass Spectrometer (ICP-MS)
High Performance Liquid Chromatograph with Tandem Mass Spectrometer (HPLC-MS/MS)
High Performance Liquid Chromatograph with Tandem Mass Spectrometer (HPLC-MS/MS)
Purge-and-Trap Gas Chromatograph Mass Spectrometer (P&T GC-MS)
Purge-and-Trap Gas Chromatograph Mass Spectrometer (P&T GC-MS)
The laboratory accredited by the Hong Kong Laboratory Accreditation Scheme (HOKLAS)
The laboratory accredited by the Hong Kong Laboratory Accreditation Scheme (HOKLAS)

In addition, the WSD has developed innovative and efficient water quality monitoring technologies, which have enhanced the department's efficiency in water safety monitoring.

Trial Use of Unmanned Surface Vessel (USV) System for Water Quality Monitoring and Sampling at Impounding Reservoirsirs
Biosensing Alert System

Drinking Water Quality Data

The WSD publishes drinking water quality data according to its monitoring results on its website. Drinking water quality data in the preceding 12-month period are published half-yearly. The drinking water quality data for the period of October 2019 to September 2020 are as follows:

The drinking water quality for this period fully complied with the Hong Kong Drinking Water Standards.

For the water quality data of DJ water, please refer to the Dongjiang Water webpage.

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