The key features include: the important principles and practices of Sanitary Engineering, as they are understood and generally applicable in our country today, have been fully delineated so that it may be easy for the students preparing for various examinations; the treatment of the subject has been kept exhaustive, sufficiently simple without sacrificing the fundamentals involved; and, effort has been made to keep the information as much up-to-date and compact as possible, and with that view, some references have been made to the relevant Indian Standard Specifications, so that to the engineers in the profession, it may also prove to be of use. The book is broadly split up into four parts. Part I deals exclusively with the subject of “Water Supply”, Part II describes “Sewerage and Sewage Treatment”, Part III “Water Supply and Drainage of Buildings” and Part IV “Environmental Sanitation”, which includes only some of the more important topics of the day viz., Refuse Sanitation, Ventilation and Air-conditioning, Air Pollution, and Malaria, incidental to Engineering. A number of selective questions of the various Indian Universities and other examinations have been given towards the end of each chapter to serve as an exercise to the problems duly solved in the chapter. The last 2-3 decades have seen tremendous research and development in the fields of water treatment and sewage/wastewater treatment. New concepts like unit operations in water treatment and unit operation and processes, in particular biological processes, in sewage/wastewater treatment have been introduced. Besides topics like defluoridation, demineralization and wastewater reclamation have evoked considerable interest and attention. To reflect these changes, this book has been revised to make it updated, with the latest information on these topics. The readers will find the book more appropriate and useful to their needs.