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Microbial Population Dynamics and Ecosystem Functions of Anoxic/Aerobic Granular Sludge in Sequencing Batch Reactors Operated at Different Organic Loading Rates

Journal article
Authors E. Szabo
R. Liebana
Malte Hermansson
O. Modin
F. Persson
B. M. Wilen
Published in Frontiers in Microbiology
Volume 8
ISSN 1664-302X
Publication year 2017
Published at Department of Chemistry and Molecular Biology
Language en
Links doi.org/10.3389/fmicb.2017.00770
Keywords microbial community dynamics, aerobic granular sludge, microbial functional groups, ecosystem functions, organic loading rate, nitrogen removal, wastewater treatment, sequencing batch reactors, waste-water treatment, biological phosphorus removal, autotrophic, nitrifying biofilms, activated-sludge, aerobic granules, simultaneous, nitrification, nutrient removal, nitrogen removal, heterotrophic, bacteria, filamentous bacteria, Microbiology, shima k, 1991, water science and technology15th biennial conf of the international assoc on water pollution research and control, jul 29-aug 03, 1990, kyoto, japan, v23, p981, ilroy sj, 2015, database oxford 0627
Subject categories Biological Sciences, Earth and Related Environmental Sciences

Abstract

The granular sludge process is an effective, low-footprint alternative to conventional activated sludge wastewater treatment. The architecture of the microbial granules allows the co-existence of different functional groups, e.g., nitrifying and denitrifying communities, which permits compact reactor design. However, little is known about the factors influencing community assembly in granular sludge, such as the effects of reactor operation strategies and influent wastewater composition. Here, we analyze the development of the microbiomes in parallel laboratory-scale anoxic/aerobic granular sludge reactors operated at low (0.9 kg m(-3) d(-1)), moderate (1.9 kg m(-3) d(-1)) and high (3.7 kg m(-3) d(-1)) organic loading rates (OLRs) and the same ammonium loading rate (0.2 kg NH4-N m-3 d(-1)) for 84 days. Complete removal of organic carbon and ammonium was achieved in all three reactors after start-up, while the nitrogen removal (denitrification) efficiency increased with the OLR: 0% at low, 38% at moderate, and 66% at high loading rate. The bacterial communities at different loading rates diverged rapidly after start-up and showed less than 50% similarity after 6 days, and below 40% similarity after 84 days. The three reactor microbiomes were dominated by different genera (mainly Meganema, Thauera, Paracoccus, and Zoogloea), but these genera have similar ecosystem functions of EPS production, denitrification and polyhydroxyalkanoate (PHA) storage. Many less abundant but persistent taxa were also detected within these functional groups. The bacterial communities were functionally redundant irrespective of the loading rate applied. At steady-state reactor operation, the identity of the core community members was rather stable, but their relative abundances changed considerably over time. Furthermore, nitrifying bacteria were low in relative abundance and diversity in all reactors, despite their large contribution to nitrogen turnover. The results suggest that the OLR has considerable impact on the composition of the granular sludge communities, but also that the granule communities can be dynamic even at steady-state reactor operation due to high functional redundancy of several key guilds. Knowledge about microbial diversity with specific functional guilds under different operating conditions can be important for engineers to predict the stability of reactor functions during the start-up and continued reactor operation.

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