This book presents high-quality peer-reviewed papers from the 3rd International Conference on Green Environmental Engineering and Technology (IConGEET), held in July 2021, Penang, Malaysia. The contents are broadly divided into four parts: (1) air pollution and climate change, (2) environment and energy management, (3) environmental sustainability, and (4) water and wastewater. The major focus is to present current researches in the field of environmental engineering towards green and sustainable technologies. It includes papers based on original theoretical, practical, and experimental simulations, development, applications, measurements, and testing. Featuring the latest advances in the field, this book serves as a definitive reference resource for researchers, professors, and practitioners interested in exploring advanced techniques in the field of environmental engineering and technologies.