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Following is a question by the Hon Albert Chan and a written reply by the Secretary for the Environment, Mr Edward Yau, in the Legislative Council today (May 28):
Question:
Recently, I have received complaints from members of the public that they often smelled stench when they were on a bus and passed by Siu Ho Wan. They suspected that the stench came from the nearby Siu Ho Wan Water Treatment Works. They have also pointed out that as members of the public and tourists must use the expressway near Siu Ho Wan to commute to and from the Hong Kong International Airport, the stench may affect public health and the image of Hong Kong. In this connection, will the Government inform this Council whether :
(a) it knows the source of the above stench; if so, of the details; if not, the reasons for that; and
(b) it has measures to ameliorate the above stench problem; if so, of the details and when the problem is expected to be resolved; if not, the reasons for that?
Reply:
Madam President,
The Siu Ho Wan Sewage Treatment Works of the Drainage Services Department (DSD) was expanded in 2005 to become a chemically enhanced primary treatment plant for treatment of sewage inflow from Discovery Bay, the Theme Park and Tung Chung. DSD attaches great importance to impacts arising from the operation of the sewage treatment works on the surrounding environment and has installed deodorising facilities in the design of the plant. Since the operation of the expanded plant, we have been conducting odour monitoring exercises about two times per week.
After receiving several enquiries on odour in 2006, DSD conducted investigation accordingly. It was found that due to the relatively long travelling time of the sewage to the plant from various sources, the septicity of the sewage was relatively high and therefore susceptible to odour emission. In order to further ameliorate the impact of odour to the neighbourhood, DSD has completed the following improvement measures:
(a) covering the sewage intakes to prevent release of odour;
(b) providing additional return liquor (generated from sludge dewatering process) pipes and installing additional deodorising facilities. Upon completion of the works, odour from return liquor has been effectively reduced;
(c) replacing the chemicals for accelerating the sedimentation of solids. Ferric chloride, which can effectively control the production of odour, is adopted; and
(d) increasing the frequency of cleaning of the sludge container and enclosed inspection, and providing extra deodorising facilities at the sludge handling area.
The above measures have improved the odour problem. In addition, DSD will commence the following works in August 2008 and monitor the progress closely to ensure completion of works in late 2009 as scheduled. The works include:
(a) providing deodorising facilities in the sludge treatment system (already in the design stage);
(b) covering other possible sources of odour such as the intake and outlet of sedimentation tanks (already in the design stage); and
(c) installing an automatic hydrogen sulphide-monitoring device in the plant for round-the-clock monitoring of the operation of the deodorising facilities to enable immediate follow up action to be done.
The above measures will further improve the plant's management of the odour problem.
Ends/Wednesday, May 28, 2008
Issued at HKT 16:15
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