During his many years at Berkeley, David taught and mentored students and post-doctoral researchers from all over the world. He supervised over 50 Ph.D. students and numerous post-docs and visiting scholars, many of whom became leaders in environmental science and engineering. He published over 250 refereed papers including a final one in 2020. His groundbreaking research into the microbiology of the activated sludge process for treating wastewater led to the development of a model and decision tree-based expert system that helps engineers design and manage the process in a manner that reduces the risks of system failures. His work improved both the cost effectiveness and operability of the activated sludge process, which has increased access to wastewater treatment to megacities of the developing world. For his work, he was recognized worldwide with numerous awards and prizes. Among the most prestigious was his election to the National Academy of Engineering in 2001. He was also Fellow of the Chartered Institution of Water Environment and Management (UK) and was conferred Honorary Life Memberships by CWEA, WEF and the International Water Association. One example of David’s sustained recognition was receiving three Water Environment Federation Harrison Prescott Eddy Medals for Research (1974, 1985, 1988) – a feat unique in the history of the award.