Promoting the Development and Application of Renewable Energy (Drainage Services Department)

"As an experienced propellant of renewable energy projects in the Drainage Services Department, I constantly ponder ways to introduce breakthrough improvements in this area for the department and our community." Drainage Services Department Senior Project Manager, Li Chung-leung, Ricky said.

"I often encourage my colleagues to proactively voice out effective and innovative methods and ideas, enabling the department to continuously enhance the renewable energy focused quality service culture. Inculcating the mindset of “You Can Do It”, we strive to overcome the challenges encountered during the application of new technologies and the operation of renewable energy facilities."

Ricky said, "I encourage them to try boldly and verify carefully, inspire and lead colleagues to pay extra effort and exert team spirit to resolve problems."

Today, the harbour in Hong Kong is so beautiful that citizens can enjoy swimming and experience the excellent water quality. This is the result of Drainage Services Department’s (DSD) years of hard work.

In addition to sewage treatment and flood prevention, DSD has been actively developing and promoting the application of renewable energy in recent years, contributing to the sustainable development in Hong Kong.

Rapid population growth coupled with the dramatic increase in economic activities have inevitably generated a large amount of sewage. DSD collects up to 2.8 million m3 of sewage every day, enough to fill up 1,120 standard size swimming pools. The collected sewage is then conveyed to sewage treatment works for treatment. The conveyance and treatment processes consume substantial amount of energy.

The four major secondary sewage treatment works in DSD have been employing the latest technology to utilise the biogas produced during the sludge treatment process to generate electricity and heat for use within the sewage treatment works.

To maximise the use of renewable energy, DSD sent staff on study visits to the United States, Germany, and other regions to learn from their experience and to explore effective ways of developing renewable energy in Hong Kong.

Ricky said, "Apart from getting our job done, we are constantly exploring ways to bring greater benefits to the environment. Taking the Tai Po Sewage Treatment Works as an example, we need to pay over a million dollars for electricity every month. Could it be self-sustainable in energy?"

Riding on the production of biogas during the sludge treatment process, DSD, in the spirit of “Daring to Try, Practising with Care”, actively explores ways to increase the production of biogas. Finally, in 2016, DSD and the Environmental Protection Department (EPD) jointly developed the “Food Waste and Sewage Sludge Anaerobic Co-digestion” Trial Scheme. As the Scheme was new to Hong Kong, the departments encountered many challenges during implementation.

Electrical & Mechanical Engineer, Drainage Services Department, Cheung Kin-kuen said, "Westerners’ diets are mostly meat-based, therefore, protein is the main component of their food waste, whereas in Hong Kong, the composition of food waste is mainly carbohydrates. To ensure the viability of this technology in Hong Kong, we commissioned a local university to conduct DNA test for micro-organisms to confirm that the technology is feasible to be applied in Hong Kong.

It is estimated that EPD will provide the Tai Po Sewage Treatment Works of DSD with a maximum of 50 tonnes food waste per day. The pre-treated food waste will undergo anaerobic co-digestion with the sewage sludge in the sewage treatment works. The Scheme utilises existing facilities of DSD, to harness the synergy effect in generating 30% more biogas and at the same time reducing the amount of digestate by 30%. The Scheme not only helps alleviate the burden on landfills, but also supplies a million kilowatt-hours of electricity to the sewage treatment works annually, which helps save around a million dollars in electricity cost annually.

In addition, DSD capitalises on its own advantages by installing photovoltaic panels at different sewage treatment works and pumping stations. Siu Ho Wan Sewage Treatment Works is equipped with over 4,200 photovoltaic panels with an installed generation capacity of 1.1 megawatt. When it came into operation in late 2016, it was the largest of its kind in Hong Kong. DSD also set up a Renewable Energy Information Centre there. Guided tours are provided with the aim of enhancing public awareness of the government’s effort in the development and application of renewable energy.

To promote wider use of solar energy, DSD is exploring the feasibility of installing hotovoltaic panels on the covers of the sedimentation tanks at the Stonecutters Island Sewage Treatment Works, which is the largest of its type in Hong Kong. However, the curvy surface of the sedimentation tank covers makes it difficult to install traditional photovoltaic panels.

The then Senior Electrical & Mechanical Engineer, Drainage Services Department, Wong Ying-ying, Regina added, "There are thin film photovoltaic panels available in the market. We installed them on the sedimentation tank Number 9 as a trial. Although we encountered different technical problems in the process, we are confident that by enhancing the design, more photovoltaic panels could be installed on the covers of sedimentation tanks."

The then Deputy Director of Drainage Services, Drainage Services Department, Mak Ka-wai, JP said, "The mission of DSD is to provide the public with world-class sewage treatment and drainage services. With a “Do it from the Heart” attitude, we strive to develop renewable energy. On average, we produce around 27 million kilowatt-hours of electricity a year, which is equivalent to 9% of our overall electricity consumption. According to statistics, Hong Kong’s potential in developing renewable energy is about 3 to 4% of the total electricity consumed. Although we have already far exceeded this figure, DSD will keep the momentum going. We hope that by around 2030, we could successfully turn the Tai Po Sewage Treatment Works into a “zero emission” facility, achieving the goal of “waste-to-energy”. I believe that with the concerted efforts of our staff, we will be able to achieve it."

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