LCQ8: Stonecutters Island Sewage Treatment Works and West Kowloon Refuse Transfer Station

     Following is a question by the Hon James To Kun Sun and a written reply by the Secretary for the Environment, Mr Edward Yau, at the Legislative Council meeting today (October 20):


     From time to time in recent years, I have received complaints from residents of the Stonecutters Island and the Yau Ma Tei Typhoon Shelter areas about odours frequently coming from the sea water.  Moreover, although government officials said at the meeting of the Panel on Environmental Affairs (EA Panel) of this Council on January 25 this year that an analysis of the water quality at the outfalls of the Stonecutters Island Sewage Treatment Works (SCISTW) indicated that the residual chlorine content was within acceptable limits, it was recently reported in a weekly magazine that the outcome of the tests and investigation conducted by it showed that the sewage discharged from SCISTW and the operation of the West Kowloon Refuse Transfer Station (WKTS) had led to water and air pollution in the district, and the hydrogen sulphide content in the air of the district had exceeded the standards of certain states of the United States.  In this connection, will the Government inform this Council:

(a) focusing on the investigation outcome in the aforesaid report, whether the authorities had, in the past five years, conducted similar studies; if they had, of the outcome; if not, whether they will conduct such studies; whether they will re-examine if the operations of SCISTW and WKTS have led to air or water pollution in the West Kowloon district, and whether they will re-assess the impact of such facilities on the health of members of the public;

(b) whether the Environmental Protection Department (EPD) has regularly monitored the contents of air pollutants (including hydrogen sulphide, etc.) in the vicinity of the aforesaid two facilities; if it has, of the locations of the monitoring points; of the relevant data obtained in each of the past three years, and whether such data exceeded any international standards;

(c) of the monitoring results of the marine monitoring stations set up by EPD around the aforesaid West Kowloon waterfront in each of the past three years; whether it had detected any deterioration in the water quality and conducted relevant investigations to ascertain if the odours from the sea water are related to water quality;

(d) of the number of complaints received by the authorities in each of the past three years about the air or water quality near SCISTW, WKTS or the Yau Ma Tei Typhoon Shelter/the West Kowloon waterfront, and among them, the number of such complaints which had been substantiated; whether government departments such as EPD and the Marine Department, etc. had prosecuted or penalized the persons or organizations involved; if they had, of the penalties imposed;

(e) whether the Government had, in the past three years, carried out regular inspections on illegal connection of sewers for discharging sewage in the West Kowloon district; if it had, of the number and locations of sewers which were proved to be illegally connected but have not yet been removed so far, as well as the number and locations of sewers which illegally discharged sewage into the harbour; and whether the Government has any plan to remove all the illegal sewers;

(f) focusing on the current odour problem in the West Kowloon district, what improvement plans the Government has, including whether it has carried out any dry weather flow interceptions works in respect of the odour problem at the Yau Ma Tei Typhoon Shelter (YMTTS), and whether it has implemented any environmental measure for the operations of SCISTW and WKTS;

(g) given that in its "Harbour Area Treatment Scheme (HATS) Stage 2A Environmental Impact Assessment Study ? Investigation" report submitted in June 2008, the Drainage Services Department (DSD) recommended enclosing or covering all the identified odour sources in the preliminary treatment works and SCISTW and discharging them into the atmosphere after treatment, when such recommendation can be implemented; given that the authorities stated at the meeting of EA Panel of this Council on July 5 2005 that in the event that the water quality objectives could not be met due to an increase in the population during the implementation of HATS Stage 2, consideration would be given to proceeding to secondary sewage treatment, whether the Government has studied the feasibility of providing secondary sewage treatment; and

(h) according to the information of the Leisure and Cultural Services Department, a large flood relief box culvert was built underground in the central part of the open space at Hoi Fan Road of Tai Kok Tsui, and the culvert with its surrounding area of 33 metres in width is classified by DSD as a drainage reserve on which quite a number of manholes for repair are distributed, of the current operation of the culvert (including the areas from which flood water is collected and where flood water is discharged), and whether water quality monitoring is conducted in the district?



(a) In early 2006, DSD commissioned an environmental impact assessment (EIA) study on HATS Stage 2A.  The EIA study, completed in mid-2008, was endorsed by the Advisory Council on the Environment and approved by the Environmental Protection Department (EPD) in October 2008.  The EIA study included an impact assessment of the odour from the Stonecutters Island Sewage Treatment Works (SCISTW).  With mathematical models, it made predictions about the odour from the SCISTW upon the completion of the HATS Stage 2A extension and improvement works.  The modelling results indicated that after implementing various odour control and mitigation measures (including covering up all the odour sources and installing deodourising devices) as recommended in the EIA study report, the level of odour in the vicinity of the premises that might be affected would meet the requirement set out in the Technical Memorandum on EIA Process.

     The Government has attached great importance to the environmental performance of the SCISTW and West Kowloon Refuse Transfer Station (WKTS).  On odour management at the SCISTW, the DSD has been upgrading relevant facilities, and has carried out a series of enhancement works over the past few years to step up odour control and mitigation measures, so as to minimise the potential odour nuisance to the public.  They include the installation of chemical deodourising spray systems at all the sludge cake unloading bays and sedimentation tanks, the provision of biofilters at the vertical discharge chambers of the sedimentation tanks, and the provision of mobile deodourisers for equipment under maintenance to control any potential odour from such equipment.  

     As for the WKTS, EPD has adopted a series of odour control measures including the air purification system for filtration and deodourisation in the waste tipping hall. The tipping hall itself is designed with negative air pressure to prevent odour from emitting to the surrounding areas. The tipped waste will be compacted and containerized in sealed containers for onward transportation to the strategic landfill by marine vessels. This method of transporting waste can minimize the environmental impact to the surrounding environment and waste will not be exposed to the atmosphere in the entire waste handling procedure. As all sewage generated from the WKTS will be discharged into sewers after proper treatment,  the operation of the WKTS would not pollute the surrounding sea water. The EPD will monitor the existing operation and strengthen the environmental management of the WKTS to ensure compliance with a series of stringent environmental parameters.

(b) An odour monitoring system has been put in place at the SCISTW.  The DSD measures the odour at the boundary of the plant and at the locations of the sedimentation tanks every month.  Based on the analysis of the DSD, the concerned level of hydrogen sulphide has not constituted undesirable impact to the nearby residents.  In response to the complaints from nearby residents, the DSD had also measured hydrogen sulphide levels at the neighbouring premises and the data showed that the nearby residents had not been affected.  The DSD will continue to closely monitor the odour from the treatment works.

     Odour control at the WKTS is monitored independently by air specialists from the Hong Kong Polytechnic University.  They monitor the odour at the periphery of the WKTS at irregular hours on a daily basis.  Based on the data, no anomaly has been detected.

(c) The EPD has set up a marine monitoring station off the coast of West Kowloon to monitor the water quality.  The monthly data cover the measurement and records of various physical and chemical properties, including dissolved oxygen, ammonia nitrogen, inorganic nitrogen and E. coli.  The compliance rate of major water quality indicators is assessed annually based on the data collected.  The monitoring results over the past three years (2007-2009) show a continuous improvement in marine water quality.  The compliance rate of marine water quality for 2009 exceeds 90%, comparing favourably with the 2008 figure.  The EPD has not received any complaint about odour from the marine water.  According to a performance verification on HATS Stage 1, effluent discharged from the SCISTW has not affected the local water quality, marine sediment and benthos.  Upon the commissioning of the advance disinfection facilities of the SCISTW in early 2010, the E. coli level in marine water on the western side of Victoria Harbour fell by 60%.
(d) The number of complaints about air and water pollution received by the EPD, DSD and MD between January 1, 2008 and September 30, 2010 is shown in the tables below:

Air Pollution     2008     2009     2010
Complaints                          (as at 30.9.2010)
-----------      ------   ------   ------------------
Sewage Treatment
Works (SCISTW)

West Kowloonˇ@ˇ@ˇ@ˇ@8ˇ@ˇ@ˇ@ˇ@ˇ@2ˇ@ˇ@ˇ@ˇ@ˇ@8
Refuse Transfer
Station (WKTS)

Yau Ma Teiˇ@ˇ@ˇ@ˇ@ˇ@0ˇ@ˇ@ˇ@ˇ@ˇ@3*        4*
Typhoon Shelter
waterfront (WKW)

*Complaints were related to black smoke from vessels and not related to odour.

Water Pollution    2008     2009    2010
Complaints                          (as at 30.9.2010)
---------------    -----    -----   -----------------
SCISTW               0        0        0
WKTS                 5        0        2
YMTTS/ WKW           2        4        2

     The relevant Government departments have followed up with all the above complaints. For those individual cases that were related to the operational issues, the EPD has requested the concerned operator to take immediate measures for improvements. In the subsequent inspections, it was found that the problems had ceased. For the majority of the remaining complaints, the sources of pollution could not be identified after taking follow-up actions. Relevant government departments will continue to closely monitor the situation.

(e) The EPD has conducted regular inspections of mis-connected sewers in West Kowloon.  The numbers of confirmed cases and locations of mis- connected sewers over the past three years (from January 1, 2008 to September 30, 2010) are shown in the table below:

             Cases of    Rectified   Cases for
             mis-        cases       which follow-up
             connection              action is
                                     being taken
             ----------  ----------  --------------
Yau Tsim        27        11          16
Mong District

Sham Shui       13         3          10
Po District

     The EPD, in collaboration with other government departments, will continue to follow up on each case with a view to rectifying all the mis-connections.

(f)&(g) The Government has installed six dry weather flow interceptors in the storm water drainage system along the upstream area of YMTTS.  They are located at the junctions of Nullah Road/Nathan Road, Portland Street/Nelson Street, Soy Street/Portland Street, Dundas Street/Portland Street, Waterloo Road/Dundas Street, and Public Square Street/Reclamation Street.  These interceptors serve to intercept effluent flow in dry seasons.  The recently completed Feasibility Study of the Review of West Kowloon and Tsuen Wan Sewerage Master Plans recommends a series of works targeting YMTTS to mitigate the existing water pollution and the associated odour problems.  They include a trial scheme for providing an odour removal system at Cherry Street Box Culvert.  Detailed design of the scheme will commence soon.

     The EPD reviews regularly the WKTSˇ¦s operation and steps up odour management and inspection within the WKTS to ensure compliance with environmental standards. Apart from the air purification system for filtration and deodourisation in the waste tipping hall, we also require washing up of the bodies of refuse collection vehicles before leaving the WKTS to prevent pollution of the surrounding area.

     To solve the odour problem at the SCISTW, the DSD has been upgrading its facilities.  A series of enhancement works have also been implemented over the past few years to step up odour control and mitigation measures, so as to minimise the generation of odour. The mitigation measures include:

(1) the installation of chemical deodourising spray systems at all the sludge unloading bays and sedimentation tanks;

(2) the provision of biofilters at the vertical discharge chambers of the sedimentation tanks; and

(3) the provision of mobile deodourisers for equipment under maintenance to control odour from such equipment.

     As a long term solution to the odour problem at SCISTW, in October 2009, the DSD awarded a works contract on providing covers for all the exposed sedimentation facilities, including sedimentation tanks, flocculation tanks, main distribution channels, effluent drop shafts and launders to eliminate odour from such facilities.  The contract also includes the provision of air extraction systems and deodourising devices to extract and purify the air from the covered areas before discharge to meet the operational safety and maintenance requirements.  The works progress has been good and we expect that all the covering works will be completed in phases by year 2012.

     Apart from the above covering works for all the exposed sedimentation tanks at the SCISTW, the extension of the SCISTW includes providing deodourising devices in all the pump rooms and sludge treatment facilities to enhance the deodourising performance.  
The Government commissioned a consultancy study in June 2010 on the planned secondary sewage treatment works under the HATS Stage 2B, including the review on the water quality, population projection and sewage flow and load.  The study will put forward recommendations on planning, funding arrangements, design and construction for HATS Stage 2B.  The Government will make reference to the findings of the study in drawing up the schedule for the implementation of HATS Stage 2B; and

(h) The box culvert system near the open space at Hoi Fan Road, Tai Kok Tsui is in operation and effective in relieving floods.   It runs from Cornwall Street near Chak On Estate to the southwest along Nam Cheong Street, passes through Tung Chau Street Park, Nam Cheong Park and the open space at Hoi Fan Road, and discharges at the seawall outlet between Hampton Place and The Long Beach.  It collects rainwater from Shek Kip Mei, Sham Shui Po and Tai Kok Tsui for direct discharge into the sea.  The EPD has set up a marine monitoring station off the coast of West Kowloon to monitor the water quality regularly. The relevant water quality monitoring results are shown in our reply in paragraph (c) above.

Ends/Wednesday, October 20, 2010
Issued at HKT 16:06