A hundred years of activated sludge: time for a rethink

Abstract

Biological wastewater treatment plants (BWWTPs) based on the activated sludge (AS) process have dramatically improved worldwide water sanitation despite increased urbanization and industrialization. However, current AS-based operations are considered economically and environmentally unsustainable. In this Perspective, we discuss our current understanding of microbial populations and their metabolic transformations in AS-based BWWTPs in view of developing more sustainable processes in the future. In particular, much has been learned over the course of the past 25 years about specialized microorganisms, which could be more comprehensively leveraged to recover energy and/or nutrients from wastewater streams. To achieve this, we propose a bottom-up design approach, focused around the concept of a “wastewater biorefinery column”, which would rely on the engineering of distinct ecological niches into a BWWTP in order to guarantee the targeted enrichment of specific organismal groups which in turn will allow the harvest of high-value resources from wastewater. This concept could be seen as a possible grand challenge to microbial ecologists and engineers alike at the centenary of the discovery of the AS process.

Both widespread PEP‐CTERM proteins and exopolysaccharides are required for floc formation of Zoogloea resiniphila and other activated sludge bacteria

“…The activated sludge (AS) process has been widely utilized for the treatment of municipal sewage and industrial wastewater around the globe for over a century (Alleman and Prakasam, 1983;Sheik et al, 2014;van Loosdrecht and Brdjanovic, 2014). The AS process is still at the heart of current sewage treatment technology (van Loosdrecht and Brdjanovic, 2014).…”

The nitrogen removal and sludge reduction performance of a multi‐stage anoxic/oxic (A/O) biofilm reactor

“…The activated sludge process is widely used in wastewater treatment and reclaims plant worldwide. The process had the beauty of stability, efficacy, and low operating cost (Rahiman Sheik, Muller, & Wilmes, 2014), and the anoxic/oxic (A/O) process is a typical example. However, the contradiction between microbial demand for carbon sources and limited substrate supply in traditional A/O processes hampers the denitrification process.…”

Control structure design for resource recovery using the enhanced biological phosphorus removal and recovery (EBP2R) activated sludge process

“…As a consequence, current trends in wastewater treatment promote resource recovery, while consider the conventional activated sludge process as a means to destroy resources (2). Under this new paradigm, several strategies and process configurations have been proposed to recover nutrients, energy and water (3).…”