This document provides an introduction to physical-chemical water treatment. It discusses the instructor, Hans van Leeuwen, and his background and research interests in wastewater treatment and bioengineering. It then covers various topics related to water treatment including ozone applications, exotic species in ports, human technological development, pollution, waterborne diseases, dissolved oxygen, biochemical oxygen demand, oxygen depletion in streams, and uses the Streeter-Phelps model to analyze an example of oxygen sag in a river.