To fulfill a need that has become apparent, this book presents some practical water pollution biological field investigative techniques and practices, procedures to solve problems, data analyses, interpretation and display, and the development and writing of the investigative report. It is written principally for the biologist inexperienced in these activities, and for sanitary engineers, chemists, attorneys, water pollution control administrators, and others who are interested in broadening their understanding of this discipline. The book considers the many aquatic environments, their biotic constituents, and the effects of various pollutants upon them. Field investigations that include forming the study objectives, planning the field study, station selection, sample collection and examination, data analyses and interpretation, and reporting the results are described. Individual water quality constituents that affect the aquatic environment are discussed. Examples of field studies on specific water pollution problems are given with the collected data presented in many graphic variations. The ability to present a clear, understandable concept to the viewer by different methods of displaying data is evaluated. Examples of field investigations, with which the author has been involved, including data collection, analyses, interpretation and display are given for organic wastes, silts, toxic wastes, acid mine drainages, eutrophication, and radioactive wastes. Investigations in marine waters are discussed. Separate chapters detail the biology of municipal water supplies and sewage treatment. Biological nuisances and slimes are discussed, as well as their control. In presenting the book's contents, over 20 years of biological field investigative experience are represented in the described field and laboratory methods, report writing, and data display. Methodology modifications presented may be of value to other professional biologists. Because the results from most problem solving investigations must be presented to the lay public to engage their support for remedial actions, reporting and data display must be clear and readily understandable. Clearness and understandability have been goals of this book.