One of the major challenges in the world is to provide clean water and sanitation for all. With 3% fresh water reserves in the earth, there are more than 1 billion people who still lack access to clean drinking water. The declining water quality has not only reduced the life expectancy of humans, but it has also contributed to the deleterious negative impacts on aquatic/marine life, flora, fauna and the ecosystem. However, with rapid technological advancements and the availability of advanced scientific instruments, there has been substantial improvement in the design and operation of water and wastewater treatment systems. Recently, these sustainable eco-technologies have been designed and operated to offer the following advantages: (i) a smaller footprint, (ii) less maintenance, (iii) >99% removal of contaminants, (iv) provides the option for resource recovery, (v) less energy consumption, (vi) minimal use of chemicals, and (vii) less investment and operational costs. This book highlights the technologies used for the removal of pollutants such as dyes, uranium, cyanotoxins, faecal contamination and P/N compounds from water environments, and shows that ecotechnologies are becoming more and more important and playing critical role in removing a wide variety of organic and inorganic pollutants from water. 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.