Our Core Responsibilities
Overview of Sewage Treatment and Sewerage System in 2018-19
Apart from stormwater drainage, one of the core services of the Department is to collect, treat and discharge sewage generated daily in Hong Kong. DSD is committed to providing world-class sewage treatment services through adopting various sewage treatment processes and advanced technologies to significantly reduce the discharge of pollutants. We also carry out regular repair and maintenance works to ensure the effective operation of our sewerage, treatment and disposal facilities. Looking ahead, we will continue to expand the coverage of the sewerage system and to improve the sewage treatment facilities to protect the water quality within Hong Kong waters and promote the sustainable development of Hong Kong.
Currently, we are operating 319 sewage treatment facilities, including 69 sewage treatment works (STWs) and 250 sewage pumping stations (SPSs). In 2018-19, we treated 1,028 million cubic metres of sewage in total, of which 7.3% underwent preliminary treatment, 73.0% chemically enhanced primary treatment (CEPT), and 19.1% secondary treatments. The remaining 0.6% underwent primary and tertiary treatments.
Hong Kong-Zhuhai-Macao Bridge Hong Kong Port Sewage Treatment Works
Hong Kong Boundary Crossing Facilities (HKBCF) is located on the artificial island at the east side of the Hong Kong International Airport. To treat the sewage produced from the passenger clearance building, public toilets and government offices, a secondary sewage treatment works was built on the artificial island and was commissioned in September 2018. The design capacity of the plant is about 2,700 cubic metres per day and the plant adopts the membrane bio-reactor (MBR) technology for sewage treatment. Sewage first passes through 25 millimetres, 6 millimetres and 2 millimetres screens. Then, organic matters, suspended solids, ammonia-nitrogen, nitrate and nitrite-nitrogen are removed from sewage by the MBR. Lastly, effluent is filtered by flat-sheet membranes. Sludge produced during sewage treatment is transported to Siu Ho Wan STW for further treatment.
Our Department continues to maintain an efficient and effective operation with regard to sewage collection, treatment and disposal. At the same time, we ensure that our facilities meet with the set environmental protection objectives. Our team of professionals, aided by advanced technology and modern facilities, is working towards providing and delivering world-class sewage collection and treatment services for Hong Kong.
Professional Laboratory Services
Professional laboratory services are imperative in ensuring treated sewage meets the statutory requirements. DSD operates a number of laboratories to provide various types of testing services. Since 1999, our Sha Tin Central Laboratory and Stonecutters Island Laboratory have been accredited for testing environmental samples (water & wastewater) under the Hong Kong Laboratory Accreditation Scheme (HOKLAS) operated by the Hong Kong Accreditation Service of the Innovation and Technology Commission (ITC). The Stonecutters Island Laboratory has also gained a chemical testing accreditation which has allowed the analysis of the main components of chemicals applied in sewage treatment since 2007. To enhance laboratory efficiency and reduce human error, automatic analysers for nutrient tests, heavy metal tests and biochemical oxygen demand (BOD) tests have been installed in the Sha Tin Central Laboratory. HOKLAS accreditation of BOD tests using automatic BOD analyzers was obtained in 2017 and the Sha Tin Central Laboratory was the first laboratory in Hong Kong to grant the accreditation in this aspect.
The adoption of the Laboratory Information Management System (LIMS) and business intelligence software, not only helps us automate laboratory work flow, but also facilitates computerised management. The consolidation of laboratory results and operation data can assist us to monitor effluent quality, facilitate effective decision making, and control the sewage treatment process.
To improve the precision of instruments, monitor water quality in meeting specified discharge requirements and the efficiency of the sewage treatment process, we carry out regular sewage sampling and analyses. During the year, 32 of our laboratory test items were accredited and more than 260,000 analyses were conducted. The analytical results of effluent quality of major sewage treatment works can be found on our website.
Planning, Design and Construction of New Sewerage Facilities
Harbour Area Treatment Scheme
The Harbour Area Treatment Scheme (HATS) is one of the most important governmental infrastructure projects in Hong Kong, aiming to improve the water quality of Victoria Harbour by collecting and treating sewage from both sides of the harbour. The project was carried out in two phases, with construction works spanning two decades at a total cost of $25.8 billion. The facilities of HATS Stage 1 and Stage 2A were fully commissioned in December 2001 and December 2015 respectively.
To improve the operational flexibility and stability of the entire HATS system, the project team spent months on the preparation and planning of the replacement of two large penstocks located at 34 metres below ground level, inside the Main Pumping Station No. 1 of the Stonecutters Island STW. To accomplish these replacement works, bypasses of the preliminarily treated sewage from the upstream preliminary treatment works into Victoria Harbour were to be carried out on up to five occasions, each not exceeding two weeks within two years (from 2018 to 2020). Since the progress of the works was not only satisfactory but beyond expectation, such large-scale replacement works were successfully completed during the third bypass in March 2019 and there is no need to carry out the fourth and fifth bypasses in the fourth quarter of 2019 and the first quarter of 2020 respectively as envisaged in the original plan.
Upgrading of Mui Wo Sewage Treatment Works
The previous Mui Wo STW was commissioned in 1985, and provided secondary treatment to sewage collected from Chung Hau area, Ngan Wan Estate and the Mui Wo Ferry Pier area. In order to cater for the forecasted increase in sewage flow due to the increase in population and extension of the village public sewerage system, we engaged a consultant in 2007 to investigate the feasibility of upgrading the design capacity of the Mui Wo STW. The investigation proposed that the design capacity of the Mui Wo STW should be increased from about 1,190 cubic metres per day to about 3,700 cubic metres per day.
Construction works commenced in 2012 and was substantially completed and commissioned in April 2018. The project cost is about $967 million. During the course of upgrading, the contractor was requested to maintain the operation of the Mui Wo STW to ensure the quality of sewage treatment. The project also includes upgrading the sludge treatment and deodourisation facilities, together with landscaping and greening of the Mui Wo STW.
Tolo Harbour Sewerage of Unsewered Areas
We are carrying out sewerage works in Sha Tin and Tai Po to improve both the water quality of Tolo Harbour and sanitation for 11 unsewered communities. The project involves building a sewage pumping station at Kau To, Shatin and laying about 12 kilometres of sewers for nine and two unsewered areas in Shatin and Tai Po respectively.
Construction works commenced in 2013 and completed in December 2018. The project cost is about $364 million.
Shek Wu Hui Effluent Polishing Plant
In line with the rapid development of North District, we will expand the treatment capacity of Shek Wu Hui STW from 93,000 cubic metres per day to 190,000 cubic metres per day in phases. The plant will be upgraded to an effluent polishing plant with tertiary treatment level. This is to ensure the discharge will comply with the stricter environmental requirements, thus protecting the ecological environment of Deep Bay. We will also take this opportunity to revamp its exterior, enhance its environmental performance and promote its educational function in water conservation so as to transform Shek Wu Hui STW into an iconic and multipurpose community facility.
Shek Wu Hui Effluent Polishing Plant is executed in stages. Advance works was commenced in mid-2015 and completed in 2019. The Main Works will be implemented in three phases starting from the third quarter of 2019 targeting for completion of the final phase by 2034. The estimated cost for advance works, investigation and design is about $500 million and the estimated cost for Main Works is about $13.2 billion.
Upgrading of San Wai Sewage Treatment Works Phase 1
In light of the increasing population in Yuen Long, Tin Shui Wai and Hung Shui Kiu, the project will increase the treatment capacity of San Wai STW from existing about 164,000 cubic metres per day to about 200,000 cubic metres per day. It will also upgrade the existing preliminary treatment of San Wai STW to chemically enhanced primary treatment with ultraviolet disinfection in order to improve the water quality in the north western water.
The project, procured through a Design-Build-Operate (DBO) contract, commenced in May 2016 and is scheduled for completion in 2020. Upon completion of construction works, the contractor will undertake the operation and maintenance of the new San Wai STW for a period of 10-15 years. The estimated project cost is about $3.14 billion.
Construction of Additional Sewage Rising Main and Rehabilitation of the Existing Sewage Rising Main between Tung Chung and Siu Ho Wan
The existing sewage rising main between Tung Chung and Siu Ho Wan is the only pipe for conveying sewage collected within the Tung Chung area and airport island to the Siu Ho Wan STW. It has been in operation for 20 years, and approaching its design life of 25 years. It is imperative to provide an additional sewage rising main to keep conveyance of the sewage, and thus allow inspection and rehabilitation of the existing one. Both rising mains are designed to meet the increased demand from the development of Hong Kong International Airport and Tung Chung New Town Extension, as well as enhancing the reliability of the sewage system.
The first works contract of the project includes the construction of sewage rising main of about 6.5 kilometres with a diameter of 1,200 millimetres and associated connection and ancillary works. The second works contract of rehabilitation works will follow upon completion of the new rising main. On completion of the works, the combined nominal capacity of the two rising mains will meet the sewage flows projected up to 2038.
Expansion of Village Sewerage
Over the years, DSD has strived to expand public sewerage systems to villages in a bid to improve hygienic conditions in rural areas, as well as the quality of nearby water bodies. Construction works for sewerage projects are currently underway in Tuen Mun, Sai Kung and the Outlying Islands.
As of March 2019, we have laid public sewerage for over 240 villages. The works for around 20 villages are underway and the schemes for around 245 villages are under planning and design.
Dry Weather Flow Interceptors at Cherry Street, Tai Kok Tsui
Polluted dry weather flow from stormwater systems running in Kowloon Tong, Mongkok and Yau Ma Tei districts becomes a major cause of the deterioration in water quality and the associated odour problem at the New Yau Ma Tei Typhoon Shelter (NYMTTS). In view of the situation, we are constructing an underground dry weather flow interceptor (DWFI) and a pumping station along the seafront of NYMTTS to intercept the polluted dry weather flow from the Cherry Street box-sulvert and deliver to Stonecutters Island STW for proper treatment and disposal.
Enhancement Works for Kwun Tong Sewage Pumping Station
To support local development of East Kowloon, the enhancement works for Kwun Tong SPS will involve the construction of an underground sewage balancing facility with a capacity of 16,000 cubic metres and provision of ventilation and odour control equipment. A landscaped deck at the roof will also be constructed to enhance the visual appearance of the pumping station and provide an open space of about 10,000 cubic metres for public recreation.
Expansion of Sha Tau Kok Sewage Treatment Works,
The existing Sha Tau Kok STW was built in 1989 and is a secondary treatment works which provides treatment to the sewage collected from Sha Tau Kok Town, Yim Liu Ha, Tsoi Yuen Kok and Sha Tau Kok Chuen before discharging into Starling Inlet. To cope with the forecast increase in sewage flow in Sha Tau Kok sewage catchment, we will reconstruct the existing Sha Tau Kok STW to increase its capacity from about 1,660 cubic metres per day to about 5,000 cubic metres per day. The project also includes construction of approximately 1.7 kilometres of submarine outfall with diameter 450 millimetres and decommissioning of existing sewage pumping station and the associated rising mains.
Yuen Long Effluent Polishing Plant
The existing Yuen Long STW serves Yuen Long Town, Yuen Long Industrial Estate and Kam Tin areas with a design capacity of 70,000 cubic metres per day. We will expand the treatment capacity of Yuen Long STW in stages to 150,000 cubic metres per day to cope with the issue of ever-increasing sewage. The plant will be upgraded to an effluent polishing plant with tertiary treatment level. This is to ensure the discharge will comply with the stricter environmental requirements, thus protecting the ecological environment of Deep Bay. We will also take this opportunity to revamp its exterior, enhance its environmental performance, adopt renewable energy and incorporate extensive greening features and provide public co-use facilities for the benefit of the local community.
Environmental impact assessment was completed and Environmental Permit was granted in April 2019. Detailed design for the upgrading works is on-going. Construction will be implemented in two stages. Subject to funding approval, the construction of Stage 1 Works is scheduled for commencement in 2020 and targeted for completion in 2027. The estimated cost for investigation and design is about $98 million while the estimated cost for Stage 1 Works is about $6.8 billion.
Relocation of Sha Tin Sewage Treatment Works to Caverns
The Sha Tin STW is to be relocated to a cavern, to be excavated in Nui Po Shan on the opposite side of Shing Mun River. This will release 28 hectares of land on the existing Sha Tin STW site for other uses and improve the living environment of the district.
The future cavern complex for the relocated Sha Tin STW will be the largest of its type ever built in Hong Kong. It will be constructed by stages, namely: site preparation and access tunnel construction; main caverns construction; upstream serverage works; sewage treatment facilities installation; and decommission and demolition of existing Sha Tin STW.
The design work was completed in phases since 2017. In October 2018, we obtained the funding approval from the Finance Committee of Legislative Council and commenced the Stage 1 works – site preparation and access tunnel construction in February 2019. While the implementation programmes of the remaining stages of construction works are still under review, the total construction period of the project is estimated to be 13 years.
|Managing Underground Drainage and Sewerage Networks|
|DSD manages about 4,700 kilometres of underground drains and sewers. These underground pipes have been in
service on average for 29 years. Over 2,030 kilometres of the underground pipes have been used for 30 years or
more, with many of them showing signs of wear and tear. Structural failure of seriously deteriorated pipes may
result in soil erosion and road subsidence, affecting the normal operation of the pipelines and bringing adverse
impacts on traffic, environment and public safety.
In view of this, in addition to regular inspections, we are striving to implement a territory-wide rehabilitation programme in a risk-based approach for the aged stormwater drains and sewers. Condition surveys and rehabilitation of high risk underground pipes are being implemented in phases. At the same time, we will study and apply various cutting-edge technologies to efficiently maintain our underground pipe networks and achieve greater cost-effectiveness of our works. In 2018-19, we rehabilitated storm drains and sewers with a total length of about 14 kilometres, at a cost of about $172 million.
Overview of Sewage Services Charges
In accordance with the “Polluter Pays” principle, the Sewage Services Charging Scheme came into effect on 1 April 1995 for all users whose premises are connected to public sewers. The sewage services charges are composed of Sewage Charge (SC) and Trade Effluent Surcharge (TES). There are currently 27 trades required to pay the TES.
Billing and Water Consumption Statistics
Among the 3.04 million water utility users in Hong Kong, about 2.82 million are required to pay the SC. Among the non-domestic users, about 29,000 are required to pay the TES, the distribution of which is as follows.
Reassessment of TES Rate and Discharge Factor
Non-domestic consumers may apply for a reassessment of the TES rate or discharge factor if they consider that their effluent strength or discharge factor is lower than the corresponding values specified by law. The reassessed TES rate is valid for 3 years.
In order to provide better services, we set up a 24- hour hotline and established performance pledges on different areas of our services and enquiries to ensure public enquiries are addressed in a timely manner. In 2018-19, we received a total of 3,468 telephone and written enquiries about our sewage services charges, of which all the written enquiries were formally replied within a month.