Application of CFD Methods to the Upgrading of an Anaerobic Digester: the Case Study of the Ontinyent-agullent Wastewater Treatment Plant

Anaerobic digestion is the most widely used of the processes in wastewater treatment plants. It treats the solids generated on the primary treatment process, converting them to a stable product for use or disposal. Its purpose is to reduce pathogens, reduce biomass quantity by partial destruction of volatile solids, and produce usable gas as byproduct. It is really important to take a deeper dive into the studies of these installations with the aim of improving working conditions and design without never forget the impact of the equipment on the environment. The use of mathematical models is not strictly necessary, but they allow us to study a big quantity of possible alternatives and situations. Thus, it is possible to have different designs before the construction of the digester, and definitely, an improvement of the resource.
However, the flow and the mixing processes in these digesters are often evaluated with experimental expensive studies or with hard analytical techniques. In addition, the analytical methods that usually are utilized are insufficient to have a correct and complete characterization of mixing and transport processes. On the other hand, in the last years there is a great improvement of numerical methods applied in this topic. Thanks to velocity and computational capacity increment, methods like “computational fluid dynamic” (CFD) allow us to develop simulation of complex hydraulic domains. In this way, this numerical method is presented today as a powerful tool, complementing advantageously experimental and analytical studies.
This project is part of a research and development agreement between the “Universidad Politécnica de Valencia” and the “Grupo Aguas de Valencia”, a company for which is conducted the study. In this work is developed the numerical part, through CFD models, to estimate a possible improvement of the working conditions of an operative anaerobic digester in Ontinyent – Valencia. The research has been conducted with the collaboration of the D.ra P. Amparo López Jiménez of the “Departamento de Ingeniería Hidráulica y Medio Ambiente” in the Universidad Politecnica de Valencia.