Overview

Ninety-three percent of Hong Kong population are connected to the public sewerage system. The quantity of sewage treated amounts to 2.65 million m³ a day. Our job is two-fold. Firstly, we must ensure that the existing sewerage network and sewage treatment facilities are operated and maintained properly and efficiently such that sewage is collected, treated and disposed of safely and to the required standard. Secondly, we need to upgrade the existing sewerage infrastructure and build new facilities to serve the territory's continual development and to satisfy the community's demand for a higher standard of environmental protection.

On sewerage infrastructure, our plans include the Harbour Area Treatment Scheme (HATS) which focuses on the collection and treatment of sewage generated from both sides of Victoria Harbour, and the other involves meeting demands and improvement as identified by 16 Sewerage Master Plans (SMP) covering the rest of the territory.

HATS Stage I was commissioned in 2001. The centralized sewage treatment plant at Stonecutters Island treats now 1.40 million m³ of sewage per day, bringing substantial improvement to water quality in the harbour area.

In order to further improve the water quality in Victoria Harbour, the Government announced in May 2005 that sewage generated on both sides of Victoria Harbour would be collected and delivered to Stonecutters Island Sewage Treatment Works (STW) for proper treatment before discharge to the sea, and Stage 2 of HATS would be carried out in two phases, Stage 2A and Stage 2B.

Apart from Victoria Harbour, other major environmental improvement facilities include the commissioning of Sha Tin STW Stage 3 Phase II Extension in 2005 and the first tertiary treatment plant, together with the effluent reuse scheme, in Ngong Ping in March 2006.

Furthermore, there are several works on sewage collection and plant expansion commenced in 2005, including the Stage 5 Upgrading of Tai Po STW and the Upgrading of Shek Wu Hui STW.

Sewage Treatment and Sewerage System

We are currently operating 269 sewage treatment facilities including 70 sewage treatment plants and 199 sewage pumping stations. Out of the 2.65 million m³ sewage treated in a day, 30% receives preliminary treatment, 53% receives chemically-enhanced primary treatment (CEPT) and 17% receives secondary treatment. And the daily quantity of sludge disposed of at the landfills was about 840 tonnes.

We are also maintaining a sewerage network of over 1,500km. As sewers are susceptible to blockage because of grease and solids in the sewage, we had implemented a preventive maintenance programme to ensure the sewers are functioning properly. In last year, over 20,000 numbers of blocked drains were cleared and a total volume of around 5,000 m3 of silt were removed from the sewers.

Progress in 2005-06

Harbour Area Treatment Scheme (HATS)

Harbour Area Treatment Scheme (HATS) is a major sewerage infrastructure in Hong Kong. The commissioning of HATS Stage 1 in December 2001, providing treatment to about 75% of the sewage from urban areas around the Victoria Harbour, has brought significant improvement in water quality to the eastern and central part of our harbour. The remaining 25% of sewage will be properly treated with further improvement to the water quality in Victoria Harbour after the commissioning of HATS Stage 2A in 2014.

Stage 2A works comprise the upgrading of the preliminary treatment works around the northern and southwestern shores of Hong Kong Island; the construction of a deep sewage conveyance system to collect and convey the currently preliminarily treated sewage from Hong Kong Island to Stonecutters Island for CEPT treatment; the expansion of Stonecutters Island STW and provision of disinfection facilities. The target is to complete the whole of Stage 2A in 2014. Stage 2B works comprises the addition of a biological treatment plant adjacent to Stonecutters Island STW to further upgrade the treatment level. The implementation programme of Stage 2B will depend upon a review of water quality trends, population forcasts and sewage flow projections to be undertaken in 2010-11.

The implementation of HATS Stage 2 is, however, contingent upon the acceptance by the community that the full recurrent costs of the scheme will be recovered through sewage charge in line with the "polluter-pays-principle". Subject to this support, the Government intends to advance part of the Stage 2A disinfection facilities for completion in 2009 to improve the water quality of the western harbour.

Since the Government's announcement in May 2005, we have commenced the planning and design of Stage 2A works, particularly the disinfection facilities and the deep tunnel sewage conveyance system, which are more time-critical components of Stage 2A works. In July 2005, we commissioned a consultancy to undertake an EIA study for the disinfection facilities to be provided at Stonecutters Island STW. We further commissioned consultancies in January and February 2006 respectively to undertake the design of the deep tunnel system and the EIA study for the whole of Stage 2A works. All these study and design tasks are progressing satisfactorily.

Sewage Treatment and Disposal Works

Sha Tin STW
Sha Tin STW is the largest secondary treatment works in Hong Kong, serving Sha Tin and Ma On Shan districts. Sha Tin STW Stage 3 Extension, at a cost of about $1.68 billion, commenced in February 2001 and is scheduled for completion in 2010. The first two phases of the Extension were completed in 2004 and 2005. Upon the completion of the Stage 3 Extension, the plant will be able to serve a population of 830,000 in the districts.

Tai Po STW
The present capacity of Tai Po STW is 88,000 m³ per day. The Stage 5 Upgrading of Tai Po STW, comprising the refitting, reconstruction and the addition of sewage treatment facilities, provides sufficient sewage treatment capacity for the on-going development of Tai Po. The works was commenced in 2005 and scheduled for completion by 2010.

Shek Wu Hui STW
Shek Wu Hui STW serves nearly 300,000 residents in Sheung Shui and Fanling. To cater for the on-going development of two districts, the upgrading of Shek Wu Hui STW started in December 2005 for completion in 2009. Upon completion of the upgrading works, the plant will be able to handle the sewage flow of the growing population in Sheung Shui and Fanling and, as a result, bringing improvement to the water quality of the nearby waters.

Pillar Point Preliminary STW
The existing Pillar Point Preliminary STW in Tuen Mun is located in the north of Tuen Mun River Trade Terminal. The current treatment processes include fine screening and aerated grit removal, with effluent discharged into the sea via twin submarine outfalls. Based on the recommendation of the Review of the Tuen Mun and Tsing Yi SMP, the plant will be upgraded with a view to coping with the projected population growth resulting from planned developments at Tuen Mun and reducing pollution loadings in the western water. The works comprise expanding the plant capacity to 525,000 m³/day (Peak Wet Weather Flow) and upgrading the treatment level to CEPT and disinfection to achieve nominal minimum removal rates of 70% for SS, 55% for BOD and 99.9% for E. coli.

A Design-Build-Operate contract arrangement has been chosen for the implementation of the upgrading works together with the subsequent operation and maintenance of the STW. A market sounding exercise was carried out in June 2006 to solicit market view and comments on the newly proposed contract management.

The First Tertiary Sewage Treatment Plant with Reclaimed Water Facilities in Hong Kong

Ngong Ping STW cum Ngong Ping Sewage Treatment Information Centre was commissioned on 18 March 2006. The Secretary for the Environment, Transport and Works, Dr Sarah Liao officiated the opening ceremony.

Ngong Ping STW is the first tertiary sewage treatment plant with reclaimed water facilities in Hong Kong with treatment capacity of 3,000 m³ per day. It adopts advanced biological, filtering and disinfection technology in the treatment of sewage. The effluent after chlorination process becomes safe and reusable reclaimed water, which is conveyed to nearby public toilets, toilets in the Ngong Ping Cable Car Terminal and associated tourist facilities for flushing use. Besides, part of the reclaimed water is used inside the treatment works for rearing aquarium fishes and controlled irrigation. The Government will review and assess the experience obtained from this pilot scheme to study the feasibility on extending the use of reclaimed water in other parts of the territory.

The Information Centre inside Ngong Ping STW introduces the processes of tertiary sewage treatment and use of reclaimed water with rich and interesting information. The public is welcomed to visit the centre.

Total Water Management

The Chief Executive put forward the Total Water Management Scheme in the 2003 Policy Address. An inter-departmental working group, led by the Water Supplies Department (WSD) with the participation of DSD and Environmental Protection Department (EPD), was established. A pilot project was implemented in the Ngong Ping STW to use reclaimed water for controlled irrigation, rearing aquarium fishes and flushing in nearby public toilets. The experience obtained from this pilot scheme will shed light on the feasibility on extending the use of reclaimed water in other parts of the territory.

Environmental Performance Target

The effect of a sewage treatment plant on the environment is best measured by the quality of its effluent. The effluent quality is regulated through a discharge licensing system whereby limitations and standards are set by EPD for parameters such as the total suspended solids, 5-day biochemical oxygen demand, ammonia nitrogen, total nitrogen and E. Coli count for indicating the amount of faecal bacterial population in the treated effluent, etc.

The environmental performance target for DSD-operated sewage treatment plants in 2005-06 is to achieve a compliance percentage of 95% in all samples tested under the self-monitoring scheme specified in discharge licence conditions. This is also the performance target in the design for most sewage treatment plants of the Department. In 2005-06, DSD handled 967 million m3 of sewage, 300,000 tonnes of sludge and removed 100,000 tonnes of biochemical oxygen demand, etc. In the meantime, a compliance record of 99.6% was achieved arising from 12,157 tests conducted in all DSD operated plants. The results reflect the effort of the operators and the level of treatment achieved.

Under the management of DSD, there are in total four major secondary sewage treatment works (i.e. Sha Tin, Tai Po, Shek Wu Hui and Yuen Long) employing the anaerobic digestion process to stabilize sludge, and producing biogas in the process. The amount of biogas generated from the four sewage treatment works is about 8 million m³ each year while 80% of the biogas is used as fuel for electricity generation within the sewage treatment works.