As problem solvers, we need to persevere and remain curious and observant of the world around us. In searching for a long-term solution for the global community, Prof. Chen looked no further than Hong Kong. He used the city as a testing ground for his innovation. As a city surrounded by the sea, Hong Kong is very special: the city relies on an extensive amount of seawater for toilet flushing. In fact, no other city in the world uses seawater for toilet flushing on the same scale that we do. But, with a population of nearly 7.5 million, we need sustainable and lasting solutions for managing our wastewater. Leading the way forward, Prof. Chen and his team have pioneered the SANI process — the sulphatereduction autotrophic-denitrification and nitrification-integrated process. Conventionally, treatment technologies make use of microbes to convert contaminants in wastewater to carbon dioxide, thereby purifying the water. This method has a by-product: for every cubic meter of sewage, 0.8 kilograms of sludge is produced. In Hong Kong, that translates to 2,000 tonnes of sludge per day — that’s a lot of sludge. Prof. Chen’s SANI process makes use of sulphatereducing bacteria, which grows slowly but decomposes the contaminants in wastewater faster, reducing our daily sludge quantities by 50%. The SANI process also halves sewage-treatment costs and land required, and it reduces greenhouse gas emissions by 35%.
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