Our society is transitioning quickly into the digital age, spurred by the development of cheap and new sensing technology, breakthroughs in computing, and the development of efficient algorithms for optimization. This transition is also visible in the field of wastewater treatment and is driving new model developments, especially by exploiting the large data sets available with many utilities. At the same time, engineering practice calls for more robust models for performance evaluation and optimization of both conventional facilities and innovative processes. This book showcases six relevant studies that highlight recent promising model developments.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.