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Spring 2013  No.23
Cleaning Up
For many people, a career spent working with sewage would be a challenge. For environmental engineer Prof Guanghao Chen, it is the adventure of a lifetime that has seen the leading international researcher and his team develop pioneering wastewater treatment technology to help solve one of the world's major issues on sustainable living

As a native son of Jiaxing, a picturesque canal water town around 100km from Shanghai, Prof Guanghao Chen has always felt an affinity for rivers, lakes, streams and seas, and respected the essential role that water has played in human civilization. Now the School of Engineering professor and his research team are set to make a revolutionary contribution of their own to development through their Sulphate reduction, Autotrophic denitrification and Nitrification Integrated (SANI) Process – one of the most remarkable technological breakthroughs in wastewater treatment in over 100 years. 

More than 10 patents related to the ideas and technology have been received or applied for, and the groundbreaking nature of the research brought a clutch of international awards in 2012. The team received three International Water Association awards, Germany's International Huber Technology Prize (second prize) and a finalists' award in Spain's World Smart Cities Awards. Prof Chen was also the first Hong Kong scholar to be elected a Fellow of the prestigious International Water Association in 2011.

Such achievements follow 18 years of strenuous research efforts, which have engaged Prof Chen since he arrived at the Department of Civil and Environmental Engineering in 1995. But they also mark a watershed where Prof Chen can now place his dream of advancing the world’s capabilities for sustainable water resources within a 10-20 year realizable framework.

"I had witnessed the impact of the pollution that went together with industrialization and development in China and destroyed plants and people's lifestyle," said Prof Chen, explaining his drive to explore the field.

"When I finished high school, I knew without hesitation I wanted to study water. I applied for postgraduate studies in this area, also without hesitation. I worked as a water engineer for three years. I am fascinated by how you can turn dirty water into clean water. I feel it is my destiny, my mission, to work in this field, to change the world to have a better future – like Steve Jobs."

The task is growing more urgent by the day. The sewage sludge produced by conventional wastewater treatments is a costly, difficult item to eliminate. In Hong Kong, for example, landfills taking sewage sludge are close to capacity and sludge incineration will be unpopular with nearby residents and further impact on air quality in the city.

SANI – known as "sludge killer" in Chinese – is a novel technology that minimizes the environmental impact of sewage treatment plants by getting rid of 90% of the sludge. The idea for such a technology was inspired by Hong Kong’s globally pioneering seawater flushing system in use for the past 50 years to help solve the city's lack of water resources. Hong Kong is the only city globally using seawater for flushing on a city scale, saving 740,000 cubic meters of freshwater per day.

Using sulphate-reducing bacteria and the sulphate in seawater as the medium to oxidize and get rid of pollutants, Prof Chen discovered he could minimize 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 four-year 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.

Changing the System

‧ Conceptual diagram of triple water supply system

Prof Guanghao Chen has been deeply connected with water throughout his life:

  • Born in the Chinese water town of Jiaxing in Zhejiang Province
  • Fortune teller uncle predicts his life will be related to water
  • Aged around 11, officially changes the "hao" character in his name to include a water element, without initially telling his parents
  • Studies environmental engineering at Zhejiang University
  • One of the second batch of national candidates to undertake postgraduate studies overseas, gaining a place on a renowned environmental program at Kyoto University in Japan
  • Immediately has to learn Japanese to a level where he can undertake postgraduate studies, including writing a PhD thesis on biological wastewater treatment in Japanese
  • After 6.5 years studying and working in Japan, headhunted by National University of Singapore. Immediately has to learn English, gaining access to additional water research knowledge
  • Joins HKUST in 1995, attracted by the presence of top names in the wastewater field, such as Prof Howard Ju Chang Huang, the research facilities and the spectacular coastal campus