The outstanding alumnus Professor Andrew Mak, Professor of Engineering Practice, Department of Chemical and Biomolecular Engineering, HKUST presented a talk to senior science students on the topic “From your coffee mug to chemical reactor–A Random Walk”. Using different numerical analysis methods, he talked about basic fluid mechanics. Then he explained the theory and process of sewage treatment. Professor Mak introduced the application of stirred tank reactor in wastewater treatment. He further explained the application of theory of aeration in treating sewage. The talk was fascinating and the students were inspired!