Water is the source of life but rising pollution due to population growth, industrialization and urbanization threaten to cause a shortage in access to fresh water. As the situation becomes more precarious, learning how to cherish limited water resources is a problem that everyone around the world needs to ponder.
Led by Professor Guanghao Chen at the Department of Civil and Environmental Engineering, the research team from the Hong Kong University of Science and Technology (HKUST) has developed a cutting edge water recycling system. It has solved the problem of sewage treatment, helping reduce cost as well as meet the increasing demand for fresh water in Hong Kong. Not only that, it has also received international recognition for the technologies used.
4 billion people, nearly two-thirds of the world’s population, face severe water shortage for at least one month every year
2.3 billion people live in countries where the water supply is inadequate and 733 million live in countries with severe water shortages, such as Pakistan, Eritrea, Turkmenistan, Botswana
By 2030, about 700 million people could be displaced by severe water shortage. In addition, conflicts have occurred in many areas with extreme and high water shortages, and water may be one of the causes of conflicts. These areas include Israel, Libya, Yemen, Afghanistan, Syria and Iraq.
Washing face, brushing teeth, washing hands, flushing… every detail of our life involves water. Hong Kong, with a population of more than seven million, produces two hundred and eighty million tons of domestic sewage every day. It is enough to fill 1,120 standard swimming pools every day. This is how much water we consume on a daily basis.
In order to effectively utilize water resources, Hong Kong has a seawater supply system that provides 80% of the population with seawater for flushing. At present, Hong Kong is one of the very few places in the world that exclusively uses seawater saving about 270 million cubic meters of fresh water every year.
Hong Kong also imports fresh water (Dongjiang water) from the Pearl River Delta and uses a dual pipe system to supply seawater for flushing (22% of total fresh water demand) but its maintenance is expensive.
How can we meet the demand for water? How can the resulting water pollution be controlled?
Professor Guanghao Chen’s research team studied Hong Kong’s water problems in two major directions. They provided two major solutions to the water resources problem, namely the “SANI” Process and “The Future Water Factory”. Read on to learn more about them!
The research team is working with Delft University of Technology in the Netherlands, the University of Cape Town in South Africa and the Airport Authority, Water Supplies Department and Drainage Services Department in Hong Kong to reduce sludge production at the source during the sewage treatment process.
To achieve it, the team transforms the environment so that slow-maturing microorganisms replace the fast-maturing ones, introducing a new microbial assemblage that significantly reduces sludge production. Known as “Sulphate reduction, Autotrophic denitrification and Nitrification Integrated (SANI)”, the abbreviation (SANI) , when enunciated, means “sludge killing” in Chinese thereby describing the technology in a different language.
Professor Chen points out that the transformation of the environment is essential to the technology: “These microorganisms themselves exist in nature, we did not add them; we introduce microorganisms that do not grow even if they eat the sludge replacing the original microorganisms that fatten up dramatically changing the equation in sewage treatment.”
The team started the research as early as 2003 and then started to go outside the laboratory in 2007 to test the new technology in the Tung Chung sewage pumping station and the Shatin sewage treatment plant respectively. The results have reduced sludge volume by 70-90%. The new technology was also found to reduce odour, energy consumption and greenhouse gas emissions as well as reduce the cost of sewage treatment and the space occupied by more than 30%. It took 18 years for the research team to achieve a new breakthrough in wastewater treatment technology.
SANI’s success has not stopped Professor Chen from studying water resources. After solving the sludge problem, he came up with another way to enhance the use of water resources with new ideas and new technologies.
“Recycled water” has become an essential part of water supply systems in many major cities around the world, ensuring fresh water supply and improving water safety. There are examples of cities around the world where wastewater is safely recycled directly or indirectly into drinking water, and there are also examples of “recycled water” in Australia and Singapore. These examples show that wastewater can be treated and returned to drinking water status and then be recycled.
With the “Future Water Factory”, Professor Chen’s research team developed a new water system that uses key technologies to convert saline effluent into a safe, reliable and affordable fresh water source. The system is named “Water cycle 4.0+”.
The project has been carried out in collaboration with the University of Hong Kong, the City University of Hong Kong, the Hong Kong Polytechnic University and the Chinese University of Hong Kong with an expected completion towards the end of 2024.
Learn more about the Four Steps to “Water cycle 4.0+” on the next page.
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