the sludge production rate. This brought a host of additional benefits, reducing energy consumption, odor and greenhouse gas emissions and cutting the cost and space required for treatment by half. The exciting breakthrough came after several years of studies that had achieved some results but not enough for Prof Chen’s high expectations. “After seven years’ work, I was still not satisfied. I had only reduced sludge by 40%. This was not even close to my dream.” Then, in 2002, Prof Mark van Loosdrecht, a good friend from Delft University of Technology in the Netherlands came to visit Prof Chen at HKUST. For the first time, Prof van Loosdrecht realized that Hong Kong was using seawater for flushing. Prof Chen recalled: “He said: ‘GH, why not think around sulphate?’ I thought: ‘Yes, there could be solution there.’ But we didn’t discuss it. I reflected on it for two years and then decided to try it at a lab scale from 2004-06. And it worked very well in the lab. No sludge. Then I took the product to departments of the Hong Kong government and they liked it. So we tried it on a pilot scale at the Tung Chung Sewage Pumping Station. This was also very successful. Now, we are going for a full-scale demonstration.” The large-scale trial has received HK$24.525 million in sponsorship from the Hong Kong government’s Innovation & Technology Fund, Drainage Services Department, and industry, the largest amount for a single local environmental project. It will begin in March and run over two years at Shatin Sewage Treatment Works at an average capacity of 1,000 cubic meters of sewage per day. Following the full-scale demonstration, Prof Chen’s target is to see the system adopted in Hong Kong and then take it to coastal cities in Mainland China and to other countries. The technology has already attracted the interest of the UNESCO-IHE Institute of Water Education, which invited Prof Chen to take part in a fouryear study. Students from around the world are applying to work with Prof Chen and major companies are showing great interest. SANI has also drawn in other top researchers in the water field. One eureka moment came during a 2008 visit to HKUST by Prof George Ekama, a globally renowned water quality expert at the University of Cape Town in South Africa. Prof Chen said: “We were in the coffee shop and I was talking about my SANI research when suddenly he leapt up and said: ‘Of course! What a fantastic idea!’” He, too, became a collaborator on the project. An extension of SANI known as the triple water supply system uses freshwater for drinking, seawater for flushing and cooling, and greywater recycling systems for air-conditioning, kitchen and laundry. This not only minimizes sludge production but reduces demand for freshwater. The Hong Kong Airport has been the first organization to put the system into use, with over 50% saving in freshwater demand, reductions in carbon dioxide emissions, and up to HK$20 million saved on electricity bills. “We are altering the language but it will take some time to alter thinking about the one-pipe system that has been in place for so many years everywhere except Hong Kong, and the cost of doing so,” Prof Chen said. “However, the issue has become so large that people are now starting to see this as a good way to maximize water use.” Bringing Prof Chen several steps closer to his dream. UP IN FOCUS 4
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