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Water Safety Plan

Water Safety Plan

1. Access to safe drinking water is essential to public health. Hong Kong enjoys one of the safest drinking water supply in the world with the quality complying fully with the World Health Organization's (WHO) Guidelines for Drinking-water Quality. The Water Supplies Department (WSD) is committed to providing a safe, clean and reliable water supply to customers in Hong Kong (HK). Stringent water treatment combined with comprehensive monitoring control of the treated water quality are essential steps in safeguarding public health. With effect from 1 August 2012, WSD has monitored the quality of our drinking water in accordance with the WHO's Guidelines for Drinking-water Quality, Fourth edition (WHO 2011) released in 2011.


2. The World Health Organization advocated for the first time in the Third edition of Guidelines for Drinking-water Quality to develop and implement a preventive Water Safety Plan (WSP) to provide an effective and proactive mechanism to ensure the safety of drinking water for the protection of public health. The WSP is based on the multiple-barrier approach and the Hazard Analysis and Critical Control Points principle to ensure the safety of drinking water supply. The plan identifies potential hazards and prevents risks of contamination of drinking water from source to consumers' taps and comprises key components including: system assessment, control measures, operational monitoring, verification, management plans, documentation and surveillance.


3. In February 2005, a working group consisting of senior professionals from various operational units in the Department was set up to develop a WSP for WSD. They assessed systematically possible risks of contamination within the water supply system, and identified control measures to minimise the risks. Based on WHO recommendations, the Department of Health and WSD have agreed on the adoption of a set of guideline values for chemical and bacteriological parameters as the health-based targets for the drinking water supply in HK.


4. The primary objectives of the WSP for the WSD are as follows:
  • Prevention of contamination of source waters;
  • Reduction or removal of contamination through water treatment processes to meet water quality targets; and
  • Prevention of contamination during storage, distribution and handling of drinking water.


5. The development of the WSP for WSD has been completed in December 2006 and the WSP is fully supported by the Advisory Committee on Water Supplies (ACWS). Implementation of the WSP has commenced in early 2007 to safeguard the quality of treated water supply which mainly includes the following aspects: protection of the valuable water resources; maintaining close liaison with relevant mainland authorities for monitoring of Dongjiang water quality; operational monitoring and control of treatment processes; verifying water quality; setting up contingency plans; and surveillance on treated water quality in conjunction with the Department of Health.


Biosensing Alert System

Enhancing the rapid and preventive water quality monitoring

Drinking water quality is stringently controlled and monitored by the Water Supplies Department (WSD). All raw (untreated) water undergoes rigorous treatment processes and disinfection at the water treatment works before supplying to the public. Water samples are taken regularly for detailed analysis but testing results for most trace analyses take time to obtain.

With a view to enhancing the capability of rapid and preventive monitoring, the Water Supplies Department (WSD) has developed an innovative Biosensing Alert System which can monitor the water quality continuously and also enable us to determine rapidly and accurately whether the water quality is safe for drinking.

Biosensing Alert System

The system integrates biological, computer, telecommunication and automation technologies.

Zebrafish.   Alert.    Light-emitting Bacteria.

Zebrafish, a new model organism used in the study of human diseases and genetics, has been selected because of its high sensitivity to contaminants which may be present in water. Through information technology and internet, the responsible officers can observe in real-time the movement of the zebrafish in the specially designed aquarium, download previously recorded videos and data, monitor and control the computer programme anytime and anywhere.

Once any abnormal activity or death of zebrafish is detected, an alert will be raised. The system not only can send alert e-mails and SMS automatically, it can also make direct phone calls to the responsible officers and at the same time trigger an autosampler to start taking water samples at preset intervals.

We will then use a rapid toxicity testing system based on the bioluminescent technology (light-emitting bacteria) to test the water samples taken. This system possesses the merits of high accuracy and sensitivity and is capable of screening over 1,000 harmful substances in water within 60 minutes with low testing unit price of about HK$50 only. After enhancing and combining the above two systems, a system featured with double protection and validation capability - the Biosensing Alert System is formed.

Benefits of the Biosensing Alert System

Zebrafish Water Quality Monitoring System.   Bioluminescent Testing Technology.


The Biosensing Alert System won the Bronze Prize of the Departmental Service Enhancement Award (Large Department Category) in Civil Service Outstanding Service Award Scheme 2013.

Relevant article:


Relevant video: 

The Civil Service Outstanding Service Video Series 2013 - Water Supplies Department Biosensing Alert Flash Format.(Cantonese with English subtitles)