ENG-2001 — Page 356

THE ENVIRONMENT

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Water and Sewerage

Water pollution has increased with urban development. Hong Kong produces more than two million tonnes of sewage every day. The lack of proper treatment for most sewage from the urban area around Victoria Harbour has resulted in poor water quality there. However, the situation has shown improvement since the partial commissioning of the Stonecutters Island Sewage Treatment Works. The concentration of sewage bacteria (E. coli) in the central harbour in 2001 was about 6 400 per 100 millilitres.

Progress has been made at bathing beaches. A combination of effective control and the provision of new sewerage has reversed a recent declining trend in the water quality at beaches.

In addition, pollution control at source is now having a positive effect, and river quality is slowly improving. The percentage of rivers in the 'good' and 'excellent' categories increased from 39 per cent in 1991 to 73 per cent in 2001, and the percentage in the 'bad' and 'very bad' categories fell from 41 per cent in 1991 to

per cent in 2001.

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Sewage Treatment and Disposal

To treat sewage from the main urban area, sewage collected by the local sewerage network on both sides of Victoria Harbour will be directed to a sewage disposal system called the Harbour Area Treatment Scheme (HATS) for treatment and disposal. The system is divided into Stage I, Stage II and Stage III/IV.

Stage I collects sewage from the urban areas of Kowloon, Tsuen Wan, Kwai Tsing, Tseung Kwan O and the north-eastern part of Hong Kong Island. The Stage I system, which includes 23.6 kilometres of collection tunnels up to 150 metres below the city, was fully completed in late 2001 and commissioning has commenced in phases. The Stonecutters Island Sewage Treatment Works began operation in 1997. It is the world's most efficient chemical enhanced primary treatment plant, removing pollutants almost as efficiently as a conventional secondary treatment plant. Upon full commissioning of the Stage I system in early 2002, the system will collect and treat some 70 per cent of the sewage that enters Victoria Harbour.

The original proposal for Stage II comprised construction of a deep tunnel from Stonecutters Island to discharge the treated effluent in oceanic waters to the south of Hong Kong.

Stage III/IV will collect sewage from the north and south-western part of Hong Kong Island and transfer the effluent to Stonecutters Island for treatment.

In the light of the experience gained during Stage I works, an International Review Panel was set up in April 2000 by the Government to examine whether the original plans remain the most cost-effective and environmentally friendly means for treating the sewage that enters Victoria Harbour. The panel members presented their report in November that year. They have recommended upgrading the treatment of sewage to tertiary level by compact sewage treatment technology. This would then allow treated sewage to be discharged within the harbour via an existing short outfall, thereby obviating the need to build the long outfall as proposed under Stage II. They have also given a number of options for Stage III/IV work for collecting sewage in Hong Kong Island, and recommended some further trials and assessments to verify their viability. In late 2001, the Government commissioned consultants to examine the