Effect of sludge age on methanogenic and glycogen accumulating organisms in an aerobic granular sludge process fed with methanol and acetate.

M Pronk,R Kleerebezem,M C M Van Loosdrecht,B Abbas

doi:10.1111/1751-7915.12292

M Pronk, R Kleerebezem + Show 2 more

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https://doi.org/10.1111/1751-7915.12292

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Journal: Microbial biotechnology	Publication Date: Jun 8, 2015
Citations: 50	License type: CC BY 4.0

Affiliation: Delft University of Technology

Abstract

The influence of sludge age on granular sludge formation and microbial population dynamics in a methanol- and acetate-fed aerobic granular sludge system operated at 35°C was investigated. During anaerobic feeding of the reactor, methanol was initially converted to methane by methylotrophic methanogens. These methanogens were able to withstand the relatively long aeration periods. Lowering the anaerobic solid retention time (SRT) from 17 to 8 days enabled selective removal of the methanogens and prevented unwanted methane formation. In absence of methanogens, methanol was converted aerobically, while granule formation remained stable. At high SRT values (51 days), γ-Proteobacteria were responsible for acetate removal through anaerobic uptake and subsequent aerobic growth on storage polymers formed [so called metabolism of glycogen-accumulating organisms (GAO)]. When lowering the SRT (24 days), Defluviicoccus-related organisms (cluster II) belonging to the α-Proteobacteria outcompeted acetate consuming γ-Proteobacteria at 35°C. DNA from the Defluviicoccus-related organisms in cluster II was not extracted by the standard DNA extraction method but with liquid nitrogen, which showed to be more effective. Remarkably, the two GAO types of organisms grew separately in two clearly different types of granules. This work further highlights the potential of aerobic granular sludge systems to effectively influence the microbial communities through sludge age control in order to optimize the wastewater treatment processes.

Highlights

Aerobic granular sludge (AGS) is a new emerging wastewater treatment technology that provides several advantages over conventional activated sludge-based systems, such as reduction of surface area, lower energy demand, lower reactor volume, easier process control and excellent effluent quality (Morgenroth et al, 1997; Wilderer and McSwain, 2004; de Kreuk and van Loosdrecht, 2006)
We investigated the conversion of methanol and acetate by AGS at 35°C, with an emphasis on preventing methanogenic conversion
The responsible methanogenic organism was identified by Denaturing Gradient Gel Electrophoresis (DGGE) as Methanomethylovorans uponensis (Pronk et al, 2015)

Summary

Introduction

Aerobic granular sludge (AGS) is a new emerging wastewater treatment technology that provides several advantages over conventional activated sludge-based systems, such as reduction of surface area, lower energy demand, lower reactor volume, easier process control and excellent effluent quality (Morgenroth et al, 1997; Wilderer and McSwain, 2004; de Kreuk and van Loosdrecht, 2006). AGS systems depend on the anaerobic uptake of carbon sources and the subsequent storage of polyhydroxyalkanoates (PHA) to prevent growth of fast growing strict aerobic heterotrophic bacteria (De Kreuk and van Loosdrecht, 2004; Weissbrodt et al, 2013a). This is a key strategy to achieve long-term stable granulation and stable nitrogen and phosphorus removal. Controlling the anaerobic solid retention time (SRT) was suggested as a potential effective method to prevent proliferation of methanogens feeding on methanol or other single carbon compounds that do not lead to storage polymer formation and are excellent precursors for biogas production (Pronk et al, 2015)

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