This book focuses on the practical understanding of microorganisms in civil and environmental engineering processes. It is designed for environmental engineers who work in wastewater treatment, solid waste treatment, soil remediation, and ground improvement. The chapters in the book are written by prominent leaders and scientists in the field of environmental microbiology and microbial technologies. The book provides insight into the functions of microorganisms in environmental engineering systems and their role in solving environmental pollution problems worldwide. It covers the latest developments in environmental microbiology and microbial technologies, providing readers with up-to-date information and research. Environmental engineers play a critical role in managing and protecting the environment. Microorganisms are essential components of environmental engineering systems, and understanding their functions is crucial for effective environmental management. This book provides valuable information on the use of microorganisms in environmental engineering systems and their role in solving environmental pollution problems.