"Problem solving in environmental engineering" is principally intended as a supplement and a complementary guide to basic principles of environmental and sanitary engineering. Nonetheless, it can be sourced as a standalone problem solving text in environmental engineering. The book targets university students and candidates taking first degree courses in construction, environmental, civil, mechanical, biomedical, and chemical engineering or related fields. The manuscript is estimated to have valuable benefits to postgraduate students and professional sanitary and environmental engineers. Equally, it is anticipated that the book will excite problem solving learning and accelerate self-teaching. By writing such a script it is hoped that the included worked examples and problems will ensure that the booklet is a treasured support to student-centered learning. To accomplish such objectives great attention was paid to offer solutions to selected problems in a well-defined, clear and discrete layout exercising step-by-step procedure and explanation of the related solution employing crucial procedures, methods, approaches, equations, data, figures and calculations.