Assessment of biomass functionalities in a biofilm membrane bioreactor (BF-MBR) targeting biological nutrient removal
High concentrations of nutrients such as nitrogen, phosphorus and organic
matter can cause serious eutrophication in receiving water bodies. In biological
wastewater treatment microorganisms remove nutrients from the
wastewater and ensure that these components in the final effluent stay at
A biofilm membrane bioreactor (BF-MBR) removing nitrogen, phosphorus
and carbon from municipal wastewater was operated for 85 days. An
assessment of the process focusing on the biomass in the various reactors
was carried out. The amount of ammonium oxidizing bacteria (AOB), nitrite
oxidizing bacteria (NOB), phosphate accumulating organisms (PAO)
and glycogen accumulating organisms (GAO) was quantified. Fluorescence
in situ hybridization (FISH), confocal laser scanning microscopy (CLSM)
and digital image processing with the software daime were used for this
purpose. Changes in the communities were compared to different operating
conditions. The effect of a decrease in the hydraulic retention time (HRT)
and diluted concentrations of nutrients in the influent were evaluated. The
correlation between filamentous bacteria and the sludge volume index was
studied. The viability of bacterial populations in a nitrifying biofilm was
The BF-MBR produced a high quality effluent in terms of chemical oxygen
demand (COD), nitrogen and total suspended solids (TSS). The system
handled well the reduction in the HRT. The removal of phosphorus was not
The microbial communities investigated by FISH analysis were present
in all samples, but their abundance varied. Substrate limitation due to
reduced nutrient loading and the activity of denitrifying bacteria in the
anaerobic reactor of the A/O bio-P process, affected the population of PAOs
negatively. Results and observations from this study suggest that for the enrichment
of PAOsin an A/O bio-P system it is crucial to have strictly anaerobic
conditions in the reactor designated for this purpose and sufficient substrate
available. When the abundance of PAOs increased, the phosphorus
removal improved. A higher decay rate was observed for PAOsthan GAOs.
It might be assumed that the high decay rate of PAOs was not caused by
the substrate competition with GAOs, but rather with denitrifying bacteria.
In this study, the abundance of GAOs and AOB seemed solely limited
by the available substrate being carbon and ammonium, respectively. The
abundance of NOB and the total nitrifying community increased despite of
periods with ammonium limitations. A live/dead analysis of the nitrifying
biofilm suggested limited diffusion rates in the deeper layers of the biofilm,
leading to cell decay. The entire microbial community investigated handled
the reduction in the HRT well.
The microbial communities of the biomass were found to be more protected
on the inside of a carrier, forming larger spherical clusters, than in
the activated sludge.
The abundance of PAOs on a carrier was found to be superior of the
amount of PAOs detected in the activated sludge surrounding the carrier in
an IFAS system. A difference in the amount of PAOs and GAOs in the two
reactors of the A/O bio-P process was also found.
Large amounts of filamentous bacteria were not observed in the A/O
bio-P system despite the high sludge volume index.
Place, publisher, year, edition, pages
Institutt for bioteknologi , 2013. , 128 p.
IdentifiersURN: urn:nbn:no:ntnu:diva-21820Local ID: ntnudaim:9612OAI: oai:DiVA.org:ntnu-21820DiVA: diva2:644218
Ostgaard, Kjetill, ProfessorIvanovic, IgorLeiknes, Tor Ove