Henriet, Olivier
[UCL]
Meunier, Christophe
[Cebedeau]
Henry, Paul
[Cebedeau]
Mahillon, Jacques
[UCL]
Aerobic Granular Sludge (AGS) represents an innovative strategy to treat wastewater. It relies upon the formation of microbial consortia held together by a self-produced exopolymeric matrix. The major advantages of this process are an excellent settling capacity and a high biomass retention derived from the growth of dense bacterial populations. Aerobic granules have been reported to settle down ten times faster than flocs and the process was accommodating a biomass concentration five times higher than that of activated sludge. Biological phosphorus removal in AGS reactors is largely performed by bacteria known as Polyphosphate Accumulating Organisms (PAOs). In aerobic or anoxic conditions, these bacteria accumulate phosphorus as intracellular poly-phosphate inclusions. The Beta-proteobacteria species Candidatus Accumulibacter phosphatis has been identified as the main actor in phosphorus removal. In AGS reactors performing enhanced biological phosphorus removal, it often represents the most abundant species with relative frequencies regularly exceeding a quarter of the bacterial population. In this study, we aimed to improve phosphorus removal in AGS sequential batch reactors by a differential selection of the granules containing the highest proportion of PAOs. The abundance of PAOs in granules with different size and density were analyzed by PCR-DGGE, pyrosequencing and qPCR. Granules with intermediate densities contained the highest proportion of Ca. A. phosphatis with a 16S rRNA gene frequency up to 48.3%, corresponding to 7.9 log PAO-specific 16S rRNA gene copies per ng DNA. On the contrary, the size of the granules had little influence on the abundance of PAOs. Starting with an acetate fed AGS reactor with unstable P removal efficiency, a modification of the purge procedure was applied to remove both the slowest and fastest settling granules and to maintain a homogeneous population of granules with intermediate densities. It resulted in the improvement and stabilization of P removal over 90 %. This microbial management procedure resulted in a shift in bacterial populations and a decrease of the bacterial diversity. This study offers a new approach of biomass management to further improve phosphorus removal in sequencing batch reactors.


Bibliographic reference |
Henriet, Olivier ; Meunier, Christophe ; Henry, Paul ; Mahillon, Jacques. Improving phosphorus removal in aerobic granular sludge processes through selective microbial management.Symposium "Microbes and the Global Change" - Belgian Society for Microbiology (Brussels, du 11/12/2015 au 11/12/2016). |
Permanent URL |
http://hdl.handle.net/2078.1/176435 |