Water pollution has increased with urban development and population growth, and Hong Kong now produces more than two million tonnes of sewage every day. The lack of proper treatment for most of the sewage from the generally older urban areas around Victoria Harbour in the past had resulted in poor water quality there. But, following the full commissioning of the first stage of the Harbour Area Treatment Scheme (HATS) at the end of 2001, there has been a marked improvement, which has been sustained.

In addition, pollution control at source has yielded positive effects, and river quality has also improved. The percentage of rivers in the 'good' and 'excellent' categories increased from 34 per cent in 1986 to 77 per cent in 2004, and the percentage in the 'bad' and 'very bad' categories fell from 45 per cent in 1986 to 17 per cent in 2004.

Sewage Treatment and Disposal

To treat wastewater from the main urban areas, sewage collected by the local sewerage network on both sides of Victoria Harbour will be directed to the HATS system for treatment and disposal. The HATS, previously known as the Strategic Sewage Disposal Scheme, is a huge project that was originally divided into four stages.

The first stage, which collects sewage from the urban areas of Kowloon, Tsuen Wan, Kwai Tsing, Tseung Kwan O and the north-eastern part of Hong Kong Island for treatment at a sewage treatment plant at Stonecutters Island, was brought into full operation at the end of 2001. In addition to the treatment plant, which some experts considered as one of the most efficient of its kind in the world, the first stage comprises a number of preliminary treatment works at collection nodes, 23.6 kilometres of conveyance tunnels up to 150 metres deep, and a tunnelled outfall which disperses the treated effluent into the western anchorage area away from core Victoria Harbour.

Since commissioning, the system has performed well. The Stonecutters Island Sewage Treatment Works, which employs a chemical treatment process, has been consistently removing about 70 per cent of the organic pollutants, 80 per cent of the solids and 50 per cent of the sewage bacteria expressed as E. coli. Since the first stage actually treats about 75 per cent of the wastewater generated in the harbour catchment, it has thus reduced the total pollution load in the harbour waters by about 50 per cent. About 600 tonnes of sludge that would otherwise have gone into that harbour each day, is now effectively being removed at the treatment works and sent to modern landfills for disposal. This has brought about marked improvements in water quality. In the harbour area waters, the levels of sewage bacteria have declined by some 50 per cent overall, dissolved oxygen has increased by 10 per cent and ammonia has declined by 25 per cent, helping to restore water quality to a more natural and ecologically healthier condition. It is also encouraging to note that some soft and hard coral communities, which are very sensitive to the quality of the marine water environment, have started to revive in Victoria Harbour, according to a survey done by a local marine conservation society.

The original proposal for the subsequent stages of the scheme envisaged collection of the remainder of the untreated sewage around the harbour (from the 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 advances in sewage treatment technologies in recent years, they recommended that instead of 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 technology and arrangement for the treatment of sewage raised a number of issues that required further study. The most important of these was whether the compact sewage treatment technology developed and applied in temperate climates could treat wastewater effectively under Hong Kong conditions, and whether it would be 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 and to study the four options suggested by the expert panel. The trials and studies confirmed that it would be technically feasible to apply the biological aerated filter system, a compact sewage treatment technology, to treat the wastewater effectively under Hong Kong conditions, and that discharging the treated effluent into the harbour using short outfall would be environmentally acceptable on a long-term basis. The trials and studies also confirmed that all four options were technically feasible and that the centralised option performed more favorably in the evaluation.

Taking into consideration the findings of the trials and studies, as well as other planning, social and financial issues, the Government proposes to implement the subsequent stages of the scheme, now collectively called HATS Stage 2, in two phases. The first phase (HATS Stage 2A) will involve building deep tunnels to bring the untreated sewage from the remaining parts of Hong Kong Island to the Stonecutters Island Sewage Treatment Works. The treatment works will be expanded to provide centralised chemical treatment for all sewage from the whole of the HATS catchment with fast track provision of disinfection. Under the second phase (HATS Stage 2B), new biological treatment facilities on a site adjacent to the existing Stonecutters Island Sewage Treatment Plant will be built. In June 2004, the Government launched a five-month public consultation exercise to gather views on the way forward for HATS Stage 2. The consultation exercise ended on November 20 and the Government is considering the views and comments received. More details on the findings of the trials and studies and the public consultation exercise 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 to cater for the present and future development needs of Hong Kong. The first set of recommended works under the Chai Wan and Shau Kei Wan SMP were completed in 1997, while the other recommended works under various SMPs are being implemented progressively.

In light of 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 pursued on a priority basis.

Sewer connections to individual properties are still in progress. Improvements in several parts of the territory continue. Under the Water Pollution Control (Sewerage) Regulation, the EPD is empowered to direct house owners to connect their wastewater pipes to new public sewers. In 2004, public sewers were laid to serve a projected population of 14 000 people. Since the regulation came into force at the end of 1995, public sewers have been put in place to serve 126 000 people.

Sewage Charges

All water users who discharge their sewage to public sewers have to pay a basic sewage charge. Also, 30 trades and industries whose effluent strength well exceeds that of domestic sewage need to pay a trade effluent surcharge to reflect the additional cost of treating their stronger effluent. These charges aim to partially recover the operation and maintenance costs of sewage collection, treatment, and disposal facilities. The Government continues to provide funds for capital costs for these facilities from its Capital Works Reserve Fund. The household sewage charge in 2004 remained at a modest level of $1.20 per cubic metre of water consumed, with an exemption for the first 12 cubic metres consumed in a four-month billing period.

Livestock Waste Pollution

Indiscriminate disposal of waste from the livestock industry was formerly one of the main causes of pollution in streams and rivers in the New Territories. Before the livestock waste control scheme began in 1987, the pollution load from livestock waste — equivalent to raw sewage from more than 1.6 million people — ended up in Hong Kong's rivers and eventually the sea. Since 1988, the Waste Disposal Ordinance has banned livestock-keeping in new towns and environmentally sensitive areas. Where they are allowed, livestock farms must have proper waste treatment systems.

Under the control scheme, livestock farmers who chose to continue in business may apply for a grant and a loan to help pay for pollution-control facilities. Since the start of the scheme in 1987, about $63 million has been paid out in capital grants. Farmers who chose to cease business could apply for an allowance, and about $883 million has been paid. Livestock waste pollution has been reduced by 97 per cent since the inception of the control scheme.

The Government provides a free livestock waste collection service resulting in a monthly average of about 5 075 tonnes of livestock waste being collected in 2004.

Bathing Beaches

Bathing beaches are an important recreational resource. To protect the health of swimmers, the Government has adopted strict standards for water quality control at bathing beaches. These standards indicate the pollution level measured in terms of E.coli (the bacteria that can indicate the presence of sewage) and were devised after a thorough study of the health risk facing local bathers. The following table shows how beaches were classified in 2003 and 2004. Beaches in the 'good' and 'fair' categories meet the Government's water quality objective for bathing.

Beach water quality gradings for open beaches are available weekly through the media and the EPD's home page.