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Following is a question by the Hon Claudia Mo and a reply by the Secretary for Development, Mr Paul Chan, in the Legislative Council today (June 29):
Question:
The annual water supply from Dongjiang (DJ) at Guangdong Province to Hong Kong accounts for almost 70 per cent to 80 per cent of Hong Kong's total demand for water consumption. It has been reported that a local media organisation earlier commissioned a university to conduct sample tests on the water quality along DJ River, and the results showed that eight out of 12 water samples contained environmental estrogens, and the level of one type of the estrogens contained in these samples might have exceeded the standards recommended by the European Union, thus exposing the public to potential health hazards. Moreover, it has been reported that the flood gates at the Shawan Interception Point in Shenzhen were opened for discharge of flood water during heavy rain from May to August last year and in May this year, which might have contaminated DJ water. In this connection, will the Government inform this Council:
(1) whether the authorities sent staff to take water samples at different locations and aqueducts in DJ River Basin in the past five years for laboratory tests to ascertain the levels of environmental estrogens in DJ water; if they did, of the results of the laboratory tests; if not, the reasons for that;
(2) whether the authorities will consider, with reference to international practices, including environmental estrogens in the list of parameters for the routine monitoring of drinking water, as well as setting monitoring standards based on the findings of scientific research, so as to safeguard public health; if they will, of the details; if not, the reasons for that; and
(3) whether the authorities have assessed the impact of the flood discharge arrangements at the Shawan Interception Point on the quality of DJ water?
Reply:
President,
Recently, there was a press report about taking water samples from the Huizhou Section of Dongjiang (DJ), the Taiyuan Pumping Station of DJ, the New Shima River of Tangxia, the Shawan River of Shenzhen and the Shenzhen Reservoir to test for estrogens. According to the report, no estrogen was found in the water samples taken from the DJ Basin relating to water supply to Hong Kong, including the Huizhou Section of DJ, the Taiyuan Pumping Station of DJ (i.e. the intake point of the dedicated aqueduct for DJ water supply to Hong Kong) and the Shenzhen Reservoir (i.e. the end point of the DJ water supply system). On the other hand, the water samples taken from the New Shima River and the Shawan River were found with estrogens. According to the report, the above-mentioned test results were obtained after concentrating the water samples by 50-fold. There are limitations on this test method. The water samples contained various substances that might offset or reinforce the effects of one another during the concentration process, thus possibly affecting the test results. As such, it is not appropriate to derive the concentration of a specific estrogen compound simply by dividing the test data of the concentrated samples by 50 times. Therefore, we consider that the applicability of the test results is dubious and should not be taken for granted.
The New Shima River is a tributary of the DJ and joins the DJ at the downstream of the intake point for supplying DJ water to Hong Kong. Therefore, the water of the New Shima River would not affect the quality of DJ water supply to Hong Kong. As for the Shawan River, it is a tributary of Shenzhen River and normally discharges first into Luofang Sewage Treatment Plant and, therefore, would not affect the quality of DJ water supply to Hong Kong.
My reply to the Hon Claudia Mo's question is as follows:
(1) While the Water Supplies Department (WSD) has not taken any water sample from the DJ River Basin or the aqueduct for DJ water supply to Hong Kong to test for estrogens, it once tested for environmental estrogens in the water sample taken from the raw DJ water as received in Hong Kong at Muk Wu Pumping Station in end 2012. The laboratory test results did not reveal any estrogen.
(2) According to the "Pharmaceuticals in Drinking-water", a study report on residual concentrations of pharmaceuticals in drinking water published by the World Health Organization (WHO) in 2012, the residual concentrations of pharmaceuticals (including endocrine disrupting chemicals such as estrogens) detected in surface water and groundwater are very low, typically less than 100 ng/l while concentrations in treated drinking-water are usually well below 50 ng/l. The WHO points out the residual concentrations of pharmaceuticals in drinking water are more than 1000-fold less than the minimum therapeutic dosage. The risk to human health arising from exposure to trace concentrations of pharmaceuticals in drinking water is minimal. Therefore, the WHO does not consider it necessary to set down guideline values for residual concentrations of pharmaceuticals in its Guidelines for Drinking-water Quality for the time being.
Routine monitoring programmes for pharmaceutical residues in water sources and drinking water are also not deemed necessary by the WHO. At present, estrogen concentrations are not listed in the parameters for routine monitoring programmes in the United States and the European Union.
Currently, the treatment facilities of the WSD, including chlorine oxidation treatment, activated carbon filtration, biofiltration and ozone dosing facilities etc. are all capable of removing estrogens in water. In light of the above, the WSD has not adopted any routine monitoring programme for residual concentrations of pharmaceuticals (including estrogens) in drinking water. That said, the WSD will continue to keep in view the latest scientific evidence and developments in this respect internationally as well as the conditions of water quality in DJ Basin and maintain close liaison with the Guangdong authorities over the DJ water supply to Hong Kong. The WSD will also consult the Department of Health as appropriate and regularly review the monitoring requirements for the quality of drinking water to ensure its safety.
(3) The WSD has been paying close attention to the floodwater discharge of the Shawan Interception Point. On the mainland side, the DJ water supply for Hong Kong passes through the Shenzhen Reservoir before reaching Hong Kong. The Shawan River lies to the north of the Shenzhen Reservoir. Before being polluted by domestic effluent, it was part of the river network that formed the catchment of the Shenzhen Reservoir. Since the completion of the wastewater interception works at the Shawan in 2003, the Shawan River no longer flows into the Shenzhen Reservoir normally. The only exception is when its water level rises steeply to the alert threshold as a result of a heavy rainstorm during the flood season. The Shenzhen authorities may then need to divert some of the diluted river flow from the Shawan River to its original river channel for discharge into the Shenzhen Reservoir for the sake of public safety.
The WSD regularly collects DJ water samples received at Muk Wu Pumping Station and various water treatment works for detailed physical, chemical, microbial, biological, radiological and toxicity analyses in order to monitor the water quality. According to the findings of the WSD's regular monitoring work, the DJ water supplied to Hong Kong is of consistently good quality and the average values of various monitoring parameters are in full compliance with the water quality requirements under the agreement of DJ water supply. But certain water quality indicators of DJ water may occasionally deviate from the stipulated values for Type II waters in the Environmental Quality Standards for Surface Water (GB3838-2002) under exceptional circumstances, such as the above-mentioned emergency floodwater discharge at the Shawan Interception Point.
For continuous enhancement of the water quality of DJ water, the Guangdong and Hong Kong authorities will maintain close liaison and take appropriate measures. The details are as follows:
(i) The Guangdong and Hong Kong authorities have put in place a notification mechanism for floodwater discharge from the Shawan Interception Point to ensure that the WSD would receive early alert about floodwater discharge and take appropriate measures accordingly, such as stepping up water quality monitoring work and adjusting chemical dosages. This would ensure that all the raw water (including the DJ water) would become fully compliant with the WHO Guidelines in respect of chemical, microbial and radiological quality after treatment at the WSD's water treatment works.
(ii) The Shenzhen authorities have been actively taking forward a comprehensive remediation project for the water environment of the Shawan River Basin to protect the water quality of the Shenzhen Reservoir. The works include desilting the river channel to improve river water quality; laying sewage pipes and expanding the sewage treatment plant to reduce direct discharge of effluent to the river, and reduce the risk of contamination of the Shenzhen Reservoir by floodwater discharge from the Shawan River etc. The whole project will take two to three years to complete. The WSD will continue to follow up with the Guangdong authorities on the status of works for improving the water quality of the Shawan River.
Thank you, President.
Ends/Wednesday, June 29, 2016
Issued at HKT 14:26
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