THE ENVIRONMENT
75 per cent of the wastewater generated in the harbour catchment, it has thus reduced the total pollution load on the harbour waters by about 50 per cent. The sludge that once flowed into the harbour each day, amounting to about 600 tonnes, is now effectively being removed at the treatment works and sent to Hong Kong's modern landfills for disposal. This has brought about marked improvements in water quality in the harbour. At the eastern end of Victoria Harbour, the levels of sewage bacteria have declined up to 95 per cent, significantly reducing public health risks. Throughout the core harbour area dissolved oxygen has increased by 10 to 20 per cent and ammonia has declined by 20 to 50 per cent, helping to restore water quality to a more natural and ecologically healthier condition.
The original proposal for the subsequent stages of the scheme envisaged collection of the remainder of the untreated sewage around the harbour (from northern and western parts of Hong Kong Island) using a similar system of deep tunnels, centralised treatment at the works at Stonecutters Island, and eventual discharge of the treated effluent, after disinfection, through a long tunnelled outfall into the deep, oceanic waters to the south of Hong Kong.
This concept was reviewed in 2000 by a panel of international experts. In their report to the Government, the experts confirmed the use of deep tunnels and centralised treatment as an acceptable and cost-effective way of dealing with sewage. However, in the light of recent developments in sewage treatment technology, they recommended that, rather than pursuing the long outfall, the Government should consider upgrading the treatment level to a very high standard, and discharging the treated effluent into the harbour on a long-term basis.
The proposal to adopt a different procedure for the treatment of sewage raised a number of issues that require further study. The most important of these was whether compact sewage treatment technology developed and applied in temperate climates can treat wastewater effectively under Hong Kong conditions, and whether it was an environmentally sustainable proposition for the relatively congested Victoria Harbour to receive large volumes of effluent, although highly treated, on a long-term basis. In late 2001, the Government initiated a series of trials and studies to address these issues. The work is substantially complete and the results will be reported around the second quarter of 2004, at which time the community will have an opportunity to discuss the findings and express views on the general preference for a way forward. More details are available at the 'A Clean Harbour for Hong Kong' website, http://www.cleanharbour.gov.hk.
Sewerage Master Plans
Hong Kong has been divided into 16 areas for which sewerage master plans (SMPs) have been drawn up. The improvement works recommended under these SMPs are being carried out in a phased sewage programme so as to cater for the present and future development needs of Hong Kong. The first sewage construction works were completed in 1997 under the Chai Wan and Shau Kei Wan SMP, while the other recommended works under various SMPs are being implemented progressively.
In light of the revised population forecasts and development proposals, the sewerage master plans for Yuen Long, Kam Tin, Central and East Kowloon, Tuen Mun, Tsing Yi, the Outlying Islands, Hong Kong Island, North District and Tolo Harbour areas have been reviewed and proposals for further upgrading works are being made.
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