To meet the goals and main purpose of conserving and protecting environment together with improving public health there is a need of practicing wastewater treatment before disposing it to water bodies such as ocean, rivers, and lakes or sometimes to bare land. So the treatment of wastewater is often a great importance especially in developing country like Tanzania. There are different technologies adopted in treating such wastewater, each having advantages and disadvantages. Waste stabilization ponds (WSPs) are large, shallow basin in which raw sewage is treated entirely by natural process involving both algae and bacteria. They are used for sewage treatment in temperature and tropical climates, and represent one of the most cost effective, reliable and easily operated methods for treating domestic and industrial wastewater. This book will show all the readers the performance of Waste Stabilization over time.