Abstract
BackgroundThe study aimed to evaluate the influence of the duration times of anaerobic phases on the bacterial biocenosis characterisation while denitrifying dephosphatation in the Integrated Fixed-Film Activated Sludge – Moving-Bed Sequencing Batch Biofilm Reactor (IFAS-MBSBBR). The experiment was conducted in a laboratory model. The study consisted of four series, which differed in terms of the ratio of the anaerobic phases.duration concerning the overall reaction time in the cycle. The anaerobic phases covered from 18 to 30% of the whole cycle duration. During the reactor performance that took 9 months, the influent and effluent were monitored by analysis of COD, TKN, NH4-N, NO2-N, NO3-N, TP, PO4-P, pH, alkalinity and the phosphorus uptake batch tests. Characterisation of the activated sludge and the biofilm biocenosis was based on fluorescent in situ hybridisation (identification of PAO and GAO) and the denaturing gradient gel electrophoresis patterns.ResultsThe organic compounds removal was high (more than 95.7%) independently of cycle configuration. The best efficiency for nitrogen (91.1%) and phosphorus (98.8%) removal was achieved for the 30% share of the anaerobic phases in the reaction time. Denitrifying PAO (DPAO) covered more than 90% of PAO in the biofilm and usually around 70% of PAO in the activated sludge. A substantial part of the polyphosphate accumulating organisms (PAO) community were Actinobacteria. The denitrifying dephosphatation activity was performed mainly by Accumulibacter phosphatis.ConclusionsHigh nutrient removal efficiencies may be obtained in IFAS-MBSBBR using the denitrifying dephosphatation process. It was found that the length of anaerobic phases influenced denitrification and the biological phosphorus removal. The extension of the anaerobic phases duration time in the reaction time caused an increase in the percentage share of denitrifying PAO (DPAO) in PAO. The biocenosis of the biofilm and the activated sludge reveal different species patterns and domination of the EBPR community.
Highlights
The study aimed to evaluate the influence of the duration times of anaerobic phases on the bacterial biocenosis characterisation while denitrifying dephosphatation in the Integrated Fixed-Film Activated Sludge – Moving-Bed Sequencing Batch Biofilm Reactor (IFAS-MBSBBR)
This paper presents the results of research on the influence of the duration of the anaerobic phases on the bacterial biocenosis performing the denitrifying dephosphatation in IFAS-MBSBBR
Effect of technological parameters on bacterial community Relevant technological factors in the nutrients removal by means of denitrifying dephosphatation that determine the effectiveness of the process are: 1) elimination of as much of the biodegradable organic compounds in the anaerobic phases as possible, 2) high-efficient nitrification ensuring a sufficiently high load of nitrates available as an ultimate electron acceptor in the respiration of Denitrifying polyphosphate accumulating organisms (PAO) (DPAO) in the anoxic conditions [11]
Summary
The study aimed to evaluate the influence of the duration times of anaerobic phases on the bacterial biocenosis characterisation while denitrifying dephosphatation in the Integrated Fixed-Film Activated Sludge – Moving-Bed Sequencing Batch Biofilm Reactor (IFAS-MBSBBR). The alternative seems to be the use of denitrifying dephosphatation, which is based on the obtainment of a specific group of organisms capable of accumulating orthophosphates in anoxic conditions with a simultaneous reduction of nitrates to nitrogen gas. The discovery of a bacterial group capable of binding the excess of phosphates under anoxic conditions and at the same time reducing nitrate or nitrite to nitrogen gas (DPAO, denitrifying polyphosphate accumulating organisms) resulted in acknowledging the possibility of using this phenomenon (denitrifying dephosphatation) to a synergistic removal of nitrogen and phosphorus from wastewater with significantly lower demand for organic carbon. Ensuring optimal conditions and the enrichment of DPAO can be difficult
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