Sustainability remains the keyword and an integral part of our vision. It is an environmental pursuit that we and our working partners adhere to strictly in delivering our work and services.

Tseung Kwan O Preliminary Treatment Works

Over a hundred teachers and students from secondary schools plant shrubs together

All about Trees

Two major tree planting ceremonies stood out in the year. On 9 April 2011, the Director of Drainage Services, Mr Chan Chi-chiu, together with the Deputy Secretary of the Development Bureau, Mrs Jessie Ting, the Chairman of Tai Po District Council, the Honourable Mr Cheung Hok-ming, the Chairman of Tai Po Rural Committee, Mr Man Chun-fai, Tai Po District Officer, Mr Lee Kwok-bun, and other Tai Po village representatives, got together for this lofty cause. More than 100 secondary school teachers and students from Tai Po also took part in planting shrubs and other green plants.

Ma Wat River Planting Event
Mr Chan Chi-chiu, Director of Drainage Services (left) planting trees with Mrs Jessie Ting, Deputy Secretary of the Development Bureau and Honourable Cheung Hok-ming, Chairman of Tai Po District Council

Tree planting at Fuk Man Road nullah improvement project site in Sai Kung

Later in the year, on 16 November, our Director, together with the Deputy Secretary of the Development Bureau, Ms Grace Lui, the Chairman of Sai Kung District Council, Mr Ng Sze-fuk, and Vice-chairman of Sai Kung Rural Committee, Mr Ho Koon-shun, and other village representatives from Sai Kung, conducted another tree planting, including planting three 'bauhinia variegate', in Fuk Man Garden, Sai Kung. Again, teachers and primary students from Sai Kung Sung Tsun Catholic School and St Andrew Catholic Primary School were invited. The event gave the youngsters an opportunity to participate in the greening of their community.

Apart from planting, we transplanted a 40-year-old tree at our Jordan Valley Box Culvert site as our efforts to conserve the environment. The project team undertook studies and trials for four months before finally moving and relocating this tree in April 2011. On that big day, the team used a 400-tonne crawler crane to manoeuvre the tree to a temporary site for nursery; the entire process took more than 10 hours. The tree will be moved to a permanent location once our project is completed. The successful transplantation reinforced not only our commitment to environmental protection but also underlined the close co-operation among members of the project team. Still on trees, the Department started a 'tree risk assessment' in January 2011 and have since inspected more than 8500 trees. The assessment of individual tree will be followed by remedial works if required. We target to complete the tree risk assessment by the end of May 2012.

Transplanting a 40-year-old 'Melia Azedarach' treePrimary school students planting shrubs together

Green Roof and Vertical Greening

On green roofing, we completed the landscaping works in our existing facilities in Shatin, Tai Po, Tuen Mun and Tseung Kwan O. In the case of Tseung Kwan O, we liaised with a local District Councillor and learnt about the aspirations of the residents for a green living environment. In response, we installed more than 700m2 of green roof at our preliminary treatment works there.

Vertical greening is another environmental protection initiative. We conducted research and studies before proceeding with vertical greening at the Shatin Sewage Treatment Works (STW), and such works are nearing completion. Already, different climbers are thriving and beautifying the surrounding environment. Our study shows that the temperature of exterior wall could drop by 7°C in the summer under the cover of vegetation. On green roof, we conducted another research with the Hong Kong Polytechnic University to study its benefits in peak runoff reduction and to also look into how it could be impacted by strong wind. Data are being collected and we expect to complete the study by 2013.

1. & 2. Green roof at Shatin STW3. Green roof at Tseung Kwan O Preliminary Treatment Works

Fish ladder in the Lam Tsuen RiverCompensatory wetland located at Shuen Wan, Tai Po

About Ecological Enhancement

The rehabilitation of the Kai Tak River, a man-made concrete drainage channel rather, began in October 2011 to enhance the river's ecological value. Borrowing the experience acquired from our earlier Ho Chung River Improvement Project in Sai Kung, our project team adopted a number of similar ecological enhancement measures for the Kai Tak River. Our efforts in this regard are prompted also by residents' aspiration for an ecological channel rather than a decked nullah.

The ecological enhancement measures to be adopted include fish shelters along the channel wall, boulders on the river bed, and the planting of trees, shrubs and trailing plants along both sides of the river. The fish shelters will provide a refuge for fish, invertebrates and other aquatic organisms during periods of rapid water flow; while the boulders will make a variety of low- and high-flow areas and will thus promote bio-diversity and micro-habitats. Other works to enhance the river's visual appeal will also be included.

In March 2012, we commenced a research and development study titled 'Eco-hydraulics Study on Green Channels — Stage 1' to get a clearer picture on the extent of environmental enhancement, such as ecological habitats and species bio-diversity, that various green channel beds, embankment and substrate designs can bring forth. The study will also cover the qualitative assessment of the hydraulic resistance and the species of the vegetation. When completed in 2013, the study will offer guidelines for the Department on its river and channel ecological enhancement works.

Existing condition of Kai Tak River

Solar panels

Energy Efficiency Initiatives

1. Use of Renewable Energy

To maximise energy saving, we have been installing renewable energy devices in our plants. Devices such as solar water heaters, PV solar panels, hybrid lamp post with solar panels, wind turbine generators as well as combined heat and power (CHP) generators, are helping to further cut energy consumption. Our STWs also allow us to recover energy from treatment processes. Currently, there are anaerobic digestion facilities in our secondary treatment works that generate about 10 million m3 of biogas a year.

In 2011-12, the Department managed to generate some 27 million kWh of electricity from the 80 per cent of the biogas produced. Biogas is a by-product from stabilisation of sewage sludge and has a greenhouse gas effect 20 times worse than carbon dioxide if released. But biogas, with a 65 per cent content of methane, is also an energy source. By 2013, when we complete all energy recovery projects, we anticipate a generation of about 33 million kWh of electricity from all the biogas our plants produced.

Hybrid lamp-posts with solar panels and wind turbine generators

2. Carbon Audits to Control Greenhouse Gas Emission

The Department takes a proactive approach in controlling greenhouse gas (GHG) emission from its facilities. We are finding out the amount of GHG released arising from our plant operation and then adopt the appropriate measures to reduce such release. At the same time, we are assessing the effectiveness of these measures. This entire process is called carbon audit.

Over the last three years, we have acquired the experience of exercising carbon audit in our sewage treatment facilities. Between 2009 and 2011, we had successfully completed carbon audits first for Shatin STW, then for Siu Ho Wan STW, followed by audits for Shek Wui Hui STW and Ngong Ping STW. Audit findings in 2011 showed that the latter two STWs emitted greenhouse gas equivalent to about 7500 and 560 tonnes of carbon dioxide.

During auditing, we identified electricity and fossil fuel consumption as the key sources for GHG emissions. We thus responded by reducing electricity consumption, improving efficiency in our plants and resorting to renewable energy. The respective remedial measures adopted included installing LED lights, using more efficient air blowers and setting up solar panels and wind turbine generators.

Armed with the experience, the Department has formulated a guideline for conducting carbon audit for sewage treatment facilities in Hong Kong. The guideline standardises the procedures and scope of such audit for the treatment facilities so that results are comparable.

The Department has also commenced carbon audits on construction projects, namely the Pillar Point STW and the Drainage Improvement Works in Pok Fu Lam, Mount Butler and Happy Valley. The two carbon audits will provide some insight into the carbon footprint of our drainage construction works.

3. Use of Electric Vehicles

The Department started a trial use of electric vehicles in 2011 and now there are four such vehicles serving different areas of work, such as transporting sewage and sludge samples from STWs to our central laboratory and to the different construction sites.

The first electric vehicle charging station with a comprehensive data logging system was commissioned at Shatin STW in early 2012. The second such station will be at Yuen Long STW in the coming summer to cater for Western New Territories. With more electric vehicles coming into service and with more data being collected, we will be in a better position to monitor the cost-effectiveness of these vehicles and to assess their long-term suitability.

4. Combined Heat and Power Generator

The Department has come a long way since 1989 when it first started to recover energy from biogas with the installation of dual-fuel generators of 1MW output capacity at Shatin STW. As the years went by and with new technology, the Department was able to better utilise the biogas produced with the launch of the first Combined Heat and Power (CHP) generator at Shek Wu Hui STW in 2006.

This CHP system generates energy from a single fuel such as biogas by means of combustion — when heat and electricity are generated simultaneously — resulting in improved energy usage efficiency. Fuelled solely by biogas, CHP is also considered to be cleaner and has a lower emission level, as compared to the dual-fuel engine generator used in the earlier years. It also has higher energy recovery efficiency, in terms of thermal and electrical energy.

The first CHP generator at Shek Wu Hui STW had a capacity for 330kW. Then two more generators, of 625kW and 635kW, were installed in Tai Po and Shek Wu Hui STWs to make further use of the biogas produced. Together, the three generators yielded about 5 million kWh of electricity a year with savings amounted to $4.4 million. The electricity generated is adequate for consumption by 770 four-member families, and represented a reduction of 3507 tonnes of carbon dioxide emission.

To improve efficiency in energy recovery and to further reduce carbon dioxide emission, the Department plans to replace the dual-fuel engines at Shatin STW with a 1400kW-CHP generator by end of 2012. Another CHP generator of 630kW is being installed at Tai Po STW so as to exhaust all the biogas produced. By the end of 2013, when all these generators are commissioned, the total output capacity of all CHPs will reach 3.6MW, with a combined recovery of 33 million kWh of electricity a year.

CHP at Tai Po STW

Implementation Plan of Application of CHP Technology in DSD