Water has become one of the most important issues of our time intertwined with global warming and population expansion. The management of water supplies and the conservation of water resources remains one of the most challenging yet exciting issues of our time. Water and wastewater treatment technologies are constantly evolving creating an increasingly sustainable industry that is one of the world's largest and most interdisciplinary sectors, employing chemists, microbiologists, botanists, zoologists as well as engineers, computer specialists and a range of different management professionals. This accessible student textbook introduces the reader to the key concepts of water science and technology by explaining the fundamentals of hydrobiology, aquatic ecosystems, water treatment and supply, wastewater treatment and integrated catchment management. This fourth edition is extensively changed throughout, with new coverage of the effects of climate change, environmental assessment, sustainability and the threat to biodiversity. The text serves as a primer for both undergraduate and graduate students in either science or engineering who have an interested in freshwater biology/hydrobiology or environmental engineering. It is also useful as a unified transitional course for those who want to span the traditional areas of engineering, biology, chemistry, microbiology or business. Professionals and consultants will also find the book a useful reference.