This book contains the selected papers from the 2023 9th International Conference on Advances in Environment Research (ICAER 2023). The conference, which was held in Singapore from March 17-19, aimed to foster communication among researchers and practitioners working in a wide variety of scientific areas with a common interest in fostering advances in environmental research and related techniques. The topics covered in this proceedings include environmental sustainability, solid waste management, wastewater and sludge treatment, environmental pollution control, environmental restoration and ecological engineering, and more. This proceedings will appeal to people working in environmental science and related areas, and particularly to postgraduates and researchers who are interested in keeping abreast with new advances in environmental research.