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LCQ1 : No SARS virus found in sewage samples collected from SCISTW


Following is a question by the Hon Frederick Fung and an oral reply by the Secretary for the Environment, Transport and Works, Dr Sarah Liao, in the Legislative Council meeting today (May 21) :-

Question :

It is learnt that sewage discharged from the Princess Margaret Hospital ("PMH") is currently delivered to Stonecutters Island Sewage Treatment Works ("SCISTW") for chemically-enhanced primary treatment, i.e. the removal of pollutants by a sedimentation process which is speeded up by adding chemical additives to the sewage. In this connection, will the Government inform this Council:

(a) of the reasons for providing only chemically-enhanced primary sewage treatment at SCISTW, and whether it will upgrade the sewage treatment level at SCISTW to the secondary level, i.e. to provide biological treatment to sewage in which organic matters are converted to stable substances by bacterial activities; if it will, of the implementation details and timetable; if not, the reasons for that;

(b) whether the authorities have drawn up specific sewage treatment procedures for the removal of possible viruses and chemical wastes in the sewage discharged from PMH; if they have, of the details and effectiveness of such procedures; if not, the reasons for that; and whether these viruses and chemical wastes have affected the health of the residents near SCISTW by way of water and wind; and

(c) of the impact of the treated sewage discharged from SCISTW on the water quality and marine ecology of Hong Kong?


Madam President,

(a) The Stonecutters Island Sewage Treatment Works (SCISTW) is part of the Harbour Area Treatment Scheme (HATS) Stage 1 constructed to provide early relief of the water pollution problem in Victoria Harbour. The chemically enhanced primary treatment (CEPT) process at Stonecutters Island removes substantial quantities of pollutants from the incoming sewage, notably about 80% of suspended solids, 70% of biochemical oxygen demand, 30% of total nitrogen, 40% of phosphorus, 60% of heavy metals and 50% of sewage indicator bacteria. Under the original plan, with the help of a deep oceanic outfall which would form part of the remaining stages of HATS, the treated sewage will be discharged in the deep fast-flowing water south of Hong Kong Island where it would be safely diluted and dispersed. In the light of the diverse views over the original HATS, the Government appointed an International Review Panel (IRP) to conduct a review of the remaining stages of HATS in 2000. Following the IRP's recommendations, we are now examining the feasibility of raising the level of treatment to include a biological process with a view to discharging the treated effluent inshore permanently. The report on the environmental and engineering feasibility of the different options proposed by the IRP should be available by the end of this year. It will then be subject to wide consultation. The way forward on the remaining stages of HATS will be decided after taking into account the views received, especially in the light of whether the community is willing to share out the costs to improve our environment.

(b) As the wastewater from Princess Margaret Hospital (PMH) and from other individual discharges within the HATS Stage 1 catchment is collected and treated by the HATS Stage 1 system alike, it is impossible to differentiate the wastewater from the PMH for special treatment at SCISTW. Nevertheless, disinfectant has been added to the toilet flushing water supply system at the PMH to ensure that the sewage generated in the hospital would be disinfected. At present, the treated effluent from SCISTW is being discharged into the western anchorage area from where it is dispersed and diluted by the water currents, well away from residents. According to a recent analysis of the sewage and marine water samples collected from the SCISTW, a fish culture zone in Ma Wan, and the bathing beach at Tung Wan of Ma Wan, no Severe Acute Respiratory Syndrome (SARS) virus was found.

(c) The HATS Stage 1 system is preventing some 600 tonnes of sludge from entering our harbour every day. The sludge produced is sent for disposal at our modern landfills. This has resulted in substantial improvements in water quality throughout the harbour with widespread reductions in nutrients and increases in dissolved oxygen. As for sewage bacteria, its levels have been substantially reduced in most parts of the harbour except for the western harbour near the outfall. As a whole, the HATS Stage 1 system has effectively improved the water quality of our harbour and brought positive impacts to marine ecology.

End/Wednesday, May 21, 2003


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