With increased commitment from the international community to reduce greenhouse gas (GHG) emissions from all sectors in accordance with the Paris Agreement, the water sector has never felt the pressure it is now under to transition to a low-carbon water management model. This requires reducing GHG emissions from grid-energy consumption (Scope 2 emissions), which is straightforward; however, it also requires reducing Scope 1 emissions, which include nitrous oxide and methane emissions, predominantly from wastewater handling and treatment. The pathways and factors leading to biological nitrous oxide and methane formation and emissions from wastewater are highly complex and site-specific. Good emission factors for estimating the Scope 1 emissions are lacking, water utilities have little experience in directly measuring these emissions, and the mathematical modelling of these emissions is challenging. Therefore, this book aims to help the water sector address the Scope 1 emissions by breaking down their pathways and influencing factors, and providing guidance on both the use of emission factors, and performing direct measurements of nitrous oxide and methane emissions from sewers and wastewater treatment plants. The book also dives into the mathematical modelling for predicting these emissions and provides guidance on the use of different mathematical models based upon your conditions, as well as an introduction to alternative modelling methods, including metabolic, data-driven, and AI methods. Finally, the book includes guidance on using the modelling tools for assessing different operating strategies and identifying promising mitigation actions. A must have book for anyone needing to understand, account for, and reduce water utility Scope 1 emissions.

Computational fluid dynamics (CFD) is a rapidly emerging field in wastewater treatment, with application to almost all unit processes. To date, it has been primarily used for evaluation of hydraulic problems at Water Resources Recovery Facilities (WRRFs). A potentially more powerful use, however, is to simulate integrated physical, chemical and/or biological processes involved in WRRF unit processes on a spatial scale and to use the gathered knowledge to accelerate improvement in plant models for everyday use, that is, design and optimized operation. In this Scientific And Technical Report (STR), the fundamentals of CFD are presented and the application of CFD for more efficient and effective design and operation of WRRFs is demonstrated. The STR’s focus is on articulating the state of practice and research and development needs. Recent developments are also emphasized, including new and emerging software and computations, model calibration and verification, sources of error, etc.