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Annual Water Quality Statistics 2020

The Water Supplies Department (“WSD”) launched the Enhanced Programme in December 2017, as one of the five components of the Action Plan for Enhancing Drinking Water Safety in Hong Kong promulgated in September 2017. The Enhanced Programme monitors the concentration of six metals, viz. antimony, cadmium, chromium, copper, lead and nickel in drinking water at consumers’ taps of randomly selected premises using the following two-tier sampling protocol:- 

Tier 1 – Random Day Time (“RDT”) sampling: the purpose is to monitor the water quality in respect of the six metals.  A 1-litre unflushed sample is randomly taken during daytime.

Tier 2 – 30-minute stagnation (“30MS”) sampling: the purpose is to verify the metal exposure of consumers in case exceedance was found in the Tier 1 RDT sample.  The tap will first be flushed for 5 minutes and then stagnated for 30 minutes.  After stagnation, a 1-litre unflushed sample will be taken.

The Enhanced Programme targets on collecting sufficient local water quality data over a period of three to five years for review of the standard values of the six metals in the Hong Kong Drinking Water Standards (“HKDWS”).  


Under the Enhanced Programme, the WSD has engaged an independent consultant to select premises randomly from all water accounts of the 18 district council (“DC”) districts in Hong Kong according to the population distribution of each DC district based on a sampling rate of eight premises per 5 000 - 100 000 people. While 664 randomly selected premises were identified for collection of water samples in 2020, the WSD suspended the Enhanced Programme from 27 January to 29 November 2020 due to the COVID-19 pandemic, and therefore only 100 of such premises1 had water samples collected in the year.

The statistics of the test results of the water samples collected in 2020 under the Enhanced Programme is summarised in Table 1 below.  

Table 1: Statistics of Monitoring Results in 2020 under the Enhanced Programme

Parameter  Minimum Maximum Average 95th percentile Standard Value Compliance of water quality with the HKDWS*
Antimony
(µg/L)		 <1 <1 <1 <1 20 ✓
Cadmium
(µg/L)		 <1 <1 <1 <1 3 ✓
Chromium
(µg/L)		 <1 <1 <1 <1 50 ✓
Copper
(µg/L)		 <3 110 20 51 2 000 ✓
Lead
(µg/L)		 <1 1 <1 <1 10 ✓
Nickel
(µg/L)		 <1 26 2 4 70 ✓

* A “✓” indicates compliance of drinking water quality with the HKDWS in all randomly selected premises based on the two-tier water sampling test results of the Enhanced Programme, i.e. the parameter will be regarded as complying with the HKDWS if (i) there is no exceedance found in RDT sample or (ii) there is no exceedance found in the 30MS sample in case the RDT sample fails.  In 2020, all RDT samples complied with the HKDWS.

An analysis of the monitoring results in 2020 under the Enhanced Programme is as below:-

  1. The maximum contents of antimony, cadmium and chromium of all RDT samples was below the reporting limit2 of <1 µg/L.  It indicates that the contents of antimony, cadmium and chromium in the drinking water at consumers’ taps in Hong Kong are very low.
  2. For copper, the maximum value and the 95th percentile among all RDT samples were 110 µg/L and 51 µg/L respectively, both of which were well below the standard value of 2 000 µg/L in the HKDWS.  It indicates that the risk of exceedance of copper content in the drinking water at consumers’ taps in Hong Kong is low.
  3. For lead, the maximum value and the 95th percentile among all RDT samples were 1 µg/L and <1 µg/L respectively, both of which were well below the standard value of 10 µg/L in the HKDWS.  It indicates that the risk of exceedance of lead content in the drinking water at consumers’ taps in Hong Kong is low.
  4. For nickel, the maximum value and the 95th percentile among all RDT samples were 26 µg/L and 4 µg/L respectively, both of which were well below the standard value of 70 µg/L in the HKDWS. It indicates that the risk of exceedance of nickel content in the drinking water at consumers’ taps in Hong Kong is low.

Overall, the test results of the water samples showed that contents of the six metals in the drinking water of all premises randomly selected for sampling under the Enhanced Programme in 2020 were all in compliance with the corresponding standard values of the HKDWS.

Please visit the webpage on Enhanced Water Quality Monitoring Programme - Annual Water Quality Statistics in 18 District Council Districts for more details.

Note:

  1. Similar to overseas practices, the shortfall in sampling due to programme suspension was not made up.
  2. Reporting limit is the lowest level within an analytical method’s operation range.
Past Summary of Water Quality Statistics: