Upflow anaerobic sludge blanket reactors

Abstract

This chapter addresses the use of upflow anaerobic sludge blanket (UASB) reactors for mainstream sewage treatment in warm climate regions. The first section presents the status of the application, highlighting the development of the third-generation UASB reactors concerning the efforts of more than three decades of continuous implementation. Next, a brief background is provided based on functioning principles and typical configurations. The following section on design procedures summarizes the most relevant criteria, in which modular gas-liquid-solid (GLS) separators play a crucial role. Based on suggested standardized dimensions and integrated process control (gas pressure and hydrostatic scum withdrawal), modular GLS separators improve the reliability of the design of (third-generation) UASB reactors treating sewage. Performance prediction for chemical oxygen demand and biochemical oxygen demand removal is addressed, as well as for effluent total suspended solid concentration. A dedicated section on the operation of full-scale UASB reactors discusses the management of sludge, scum, biogas and diffuse emissions. Aspects related to design, construction and operation are explored, pointing out the main hurdles and consolidated solutions. The chapter ends with final reflections on the advances made so far and the remaining bottlenecks, stressing the key role of mainstream sewage treatment for circular economy models.