Frontier technology in water treatment and pollutant removal is needed not only for maximizing water reuse but also for the rapid detection of contaminants in the recycled water. The UN announced the years 2018 to 2028 as the 'International Decade for Action-Water for Sustainable Development'. To realize this mission, innovative and frontier technologies for water treatment and pollutant removal are important components. This book aims to serve as a platform for updating the scientific community with recent progress in this area, covering frontier technologies in analytical technique, physicochemical treatment, chemical treatment, and biological treatment. In Focus - a book series that showcases the latest accomplishments in water research. Each book focuses on a specialist area with papers from top experts in the field. It aims to be a vehicle for in-depth understanding and inspire further conversations in the sector.