Greening and Conserving Ecology
Overall Greening Works in DSD Facilities
In 2012-13, our Department continued to make all efforts in carrying out greening work in various projects, including the incorporation of green roofs in new projects and existing facilities. During the year, we planted more than 3,300 trees and 560,000 shrubs, and provided an additional 3,200 square metres of green roofs in various facilities.
Area of Green Roof Added
Upcoming Greening and Beautification Works in Stonecutters Island Sewage Treatment Works under Harbour Area Treatment Scheme Stage 2A
Stonecutters Island Sewage Treatment Works (SCISTW) is in a prominent location close to western Kowloon. It is overlooked by the public from the high rise developments around Lai Chi Kok and Tai Kok Tsui from its North and East. The Southwest of the site is screened by a lushly vegetated woodland. Environmental improvement works have been introduced to reduce the visual impact of the site as follows.
- Elevation treatments
- Soft landscaping along site roads and roofs to strengthen the greening effect
- Covering of the sedimentation tanks with randomly coloured pattern
- Carrying out BEAM (Building Environmental Assessment Method) Plus assessment
Greening Works and Ecological Conservation Measures at Tai Po
The drainage improvement works at Tai Po not only alleviate the local flooding risk but also make valuable contribution to the local greening efforts. To preserve the ecological values of existing rivers, our engineers have integrated various environmentally friendly elements into our drainage facilities, which are outlined below.
- Simulation of Existing River Characteristics
- Planting along River Channel
- Retaining the Existing River Bed
- Protection of Existing Ecological System
Energy Management and Emission Control
Conducting Carbon Audit
We conducted the first carbon audits for Tai Po STW and Stonecutters Island STW in 2012. We continued to conduct carbon audits for Shatin STW and Shek Wu Hui STW during the year to better manage our carbon footprint.
Looking forward, DSD will conduct carbon audits and adopt carbon emission reduction measures at more STWs and construction works with a view to reducing DSD's carbon footprint, making it more environmentally friendly while also providing high quality drainage and sewage treatment services to the public.
Use of Electric Vehicle
To support the latest development of green transportation and sustainable development of Hong Kong, we have taken every opportunity to promote the use of electric vehicle(EV). As EV is powered by batteries without involving any combustion process, its greatest advantage is producing zero emissions and helping improve roadside air quality in Hong Kong. At present, there are eight EVs in our fleet. With more experience accumulated in the application of EVs, we target to promote a wider use of EVs in our projects.
Implementing Various Energy Saving Measures
We have managed to save more than 11 million kilowatt-hour (kWh) electricity over the last five years. This is achieved with the implementation of measures including the optimisation of sewage treatment processes, the use of combined heat and power (CHP) plants at various sewage treatment works, the replacing of T8 fluorescent lamps and outdoor lights with T5 lamps and LED respectively at various plants, as well as the use of high-efficiency pump motors in our treatment facilities. The largest contributors to energy saving in 2012-13 were the co-settling and optimisation of sludge treatment processes at Shatin STW and the utilisation of biogas for the CHP plants at Shek Wu Hui STW.
Use of Renewable Energy
In addition, we have also implemented different large-scale stand alone or grid-connected photovoltaic (PV) systems supplying electricity to part of the equipment at our various major facilities, e.g. Yuen Long STW, Shek Wu Hui STW, Sandy Bay PTW, Stonecutters Islands STW, etc. In the coming two years, we are going to install PV panels in five other sewage treatment facilities with a total capacity of 39 kW.
Taking note that biogas from anaerobic digestion of sludge generated from sewage treatment is a renewable energy source, we looked into a better way to utilise the biogas generated including installation of combined heat and power (CHP) generators and Micro-Turbine in our plants in the past decade. We are installing new CHP generators in Shatin and Tai Po STWs, and Micro-Turbine in Yuen Long STW. Together with other recently installed CHP generators at Tai Po STW and at Shek Wu Hui STW, we foresee a full utilisation of all biogas generated from our sewage treatment works in 2013.
Installation of porous pavement and rainwater harvesting system
We understand that water is one of the most valuable resources and to make the best use of water resources in the pursuit of our sustainable development, we adopted the most appropriate water conservation measures in our facilities and projects. For example, porous pavement and rainwater harvesting system were installed in 2012-13 at the two sewage pumping stations (SPSs) in Kowloon City which enable extensive green coverage and saving of water for irrigation.
Use of Green Materials/ Products
Besides, we are currently using a number of green materials and products in our operations. These include:
- Recycled glass cullet as recycled glass block and paving block, pipe bedding materials, ingredients of blinding concrete and porous drainage materials;
- Reclaimed water;
- Synthetic manhole covers, synthetic gully gratings (both for use in nonvehicular access/area within the boundaries of Sewage Treatment Works and Pumping Stations) and PVC floor materials, in particular products containing recycled materials; and
- Recycled timber.
Green Procurement and Green Office
Our Department has actively supported the Government's initiatives on green procurement. We have purchased a wide variety of products following the green procurement specification in 2012-13, ranging from electrical appliances such as computers, copying machines, printers, electric fans and refrigerators to office consumables including recycled paper, correction tapes, pencils, rechargeable batteries, toilet paper and garbage bags.
Over the years, we have implemented a number of energy saving and resource conservation measures in our office. These include setting the room temperature at 25.5 degree Celsius, de-lamping unnecessary lights, installing timers to switch off common office equipment after office hours. We have also set up recycling stations to collect cartridge toners, rechargeable batteries, papers, plastic and metal containers. To further raise the awareness amongst our staff, we have regularly disseminated green tips and conducted environmental inspections in our workplace. With the fast development of wireless communication technology, we have introduced a "paperless meeting" system, using electronic gadgets such as tablet computers and notebooks for presentations and discussions. Paper consumption has continued to drop since 2009-10. Paper usage in 2012-13 was about 11,000 reams, a 21 per cent reduction compared to 2009-10.
Three-step mitigation measures for odour control are taken at the existing sedimentation tanks of SCISTW:
- Installation of fibreglass reinforced plastic (FRP) covers with a gasseal design on the existing sedimentation tanks, flow channels and chambers;
- Installation of an air extraction system to collect foul gas within the covered tanks, channels and chambers; and
- Treatment of foul gas by "Biotrickling Filter" technology before discharge into open air. The "Biotrickling Filter" is a reliable and environmentally friendly biological odour removal technology with a low life-cycle cost and minimum operation and maintenance requirements. It can remove 99 per cent or more of hydrogen sulphide gas (H2S), the main source of odour in STW, for effective odour control.