FEATURE: RESIDUES TO RESOURCES UNLIKE ANY OTHER THE ENVIRONMENTAL PROTECTION Department (EPD) of Hong Kong had a not-so-unique challenge: what to do with the mounting volume of sludge from wastewater treatment plants. The EPD’s solution to this problem however was anything but ordinary. An island of sludge Over 90 percent of Hong Kong’s population is served by a public sewer system with the sewage sent to wastewater treatment plants. The sludge from the treatment process has traditionally been disposed of at three landfills on the island. While it seems that all growing metropolitan areas have the challenge of disposing of municipal sludge, the fact that Hong Kong is an island makes land availability even more critical. In just a few short years, the sludge volume that Hong Kong generates has nearly doubled to about 1 000 tonnes per day. Moreover it is predicted to continue increasing, thus in the long-term landfilling of sludge will not be an environmentally sustainable option. In order to deal with this ever-expanding need for sludge disposal and to relieve the pressure on landfill capacity, a unique sludge treatment facility has been built in Tuen Mun on the northwest part of the island. Unique development The EPD awarded the US$ 660 million Design-Build-Operate contract to Veolia Water and Veolia Environmental Services. Veolia will also operate the plant for a period 12 Bioenergy International No 82, 6-2015 of 15 years. Emmanuel Toulan, Project Director for Veolia Water Solutions, joined the project in 2010. He has years of international project experience in many different industries. – I am supported here by a very large team, I was involved very heavily in the design and procurement stages, while the construction is primarily overseen by our partners at Leighton and John Holland, said Toulan. ANDRITZ Energy & Environment (AE&E) was awarded the contract to supply four EcoFluid bubbling fluidised bed (BFB) steam boilers, which form the heart of the power plant. The power plant uses wastewater sludge as fuel. Not only does this generate low-cost electrical power, it also eliminates the cost and space required to landfill the sludge. – What makes this plant unique – in addition to its large size – is the building design, degree of self-sufficiency, and educational purposes, explained Toulan. Design. The wave-like shape of the buildings makes harmonies with the sea and mountains. The plant meshes beautifully with its location next to Shenzhen Bay. Self-sufficiency. The plant is not connected to a potable water network or a public sewer system. Seawater is desalinated in an on-site plant. Rainwater is also collected and used as process water. The plant has its own wastewater treatment system to eliminate discharges to the sea. Energy generated from the plant will exceed the needs of the plant and surplus energy will be supplied to the public power grid. Educational purpose. In addition to the technological advances, the site is being constructed as an architectural and cultural landmark for Hong Kong. A unique aspect is the concept of including ecological education and leisure space for the public. An auditorium, conference centre, exhibition space, spa, coffee house, shops, and ecologically arranged gardens provide attractions for the public. A view of the bay, including the city of Shenzhen on mainland China across the bay, is available from an observation platform in the administration building – being built around the boiler stacks. Power from sludge – All of Hong Kong’s sewage treatment facilities together produce close to 1 000 tonnes per day of A very special sludge treatment plant Aesthetically pleasing, technically advanced, and open to visitors – not terms normally associated with a sewage sludge treatment plant. Then again this 110 MW thermal capacity combined heat and power (CHP) facility in Hong Kong is anything but your average plant. The Environmental Protection Department of Hong Kong provided funding for this unique sludge treatment facility in Tuen Mun on the northwest part of the island. The city of Shenzhen (mainland China) is in the background. 12 Bioenergy International No 82, 6-2015
Bioenergy no 6 October 2015
To see the actual publication please follow the link above