Granulation and microbial community dynamics in the chitosan-supplemented anaerobic treatment of wastewater polluted with organic solvents

The effect of chitosan on the development of granular sludge in upflow anaerobic sludge blanket reactors (UASB) when treating wastewater polluted with the organic solvents ethanol, ethyl acetate, and 1-ethoxy-2-propanol was evaluated. Three UASB reactors were operated for 219 days at ambient temperature with an organic loading rate (OLR) of between 0.3 kg COD m−3 d−1 and 20 kg COD m−3 d−1. One reactor was operated without the addition of chitosan, while the other two were operated with the addition of chitosan doses of 2.4 mg gVSS−1 two times. The three reactors were all able to treat the OLR tested with COD removal efficiencies greater than 90%. However, the time required to reach stable operation was considerably reduced in the chitosan-assisted reactors. The development of granules in the reactors with chitosan was accelerated and granules larger than 2000 μm were only observed in these reactors. In addition, these granules exhibited better physicochemical characteristics: the mean particle diameter (540 and 613 μm) was approximately two times greater than in the control reactor (300 μm), and the settling velocities exceeded 35 m h−1. The extracellular polymeric substances (EPS) in the reactors with the chitosan was found to be higher than in the control reactor. The protein-EPS content has been correlated with the granule size. The analyses of the microbial communities, performed through denaturing gradient gel electrophoresis and high-throughput sequencing, revealed that the syntrophic microorganisms belonging to genus Geobacter and the hydrogenotrophic methanogen Methanocorpusculum labreanum were predominant in the granules. Other methanogens like Methanosaeta species were found earlier in the chitosan-assisted reactors than in the control reactor

Effects of extraction procedures on metal binding properties of extracellular polymeric substances (EPS) extracted from anaerobic granular sludges

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Characterization of the mineral fraction associated to extracellular polymeric substances (EPS) in anaerobic granular sludges

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Effect of substrate feeding on viscosity evolution of anaerobic granular sludges

This work aims to describe the effect of the feeding regime of anaerobic activity tests on the limit viscosity (mlim) evolution of the granules. Batch experiments were performed with 3 different sources of substrate: acetate, peptone, and glucose. Despite, the substrate origin was shown to affect the mlim evolution of granules, no clear relationship was found between the mlim evolution, type of substrate and other granule physico-chemical characteristics (i.e. pH; % of Volatile Suspended Solid; concentration of exopolymeric substances, divalent cations, P and S). The origin of granules and the substrate feeding regime modify the surface shape of the granules and may change granule-granule interactions under a shear stress, thus affecting the evolution of the mlim value during long term reactor operation

Sorption of Cd(II) and Pb(II) by exopolymeric substances (EPS) extracted from activated sludges and pure bacterial strains: Modeling of the Metal/Ligand ratio effect and role of the mineral fraction

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Characterization of the mineral fraction associated to extracellular polymeric substances (EPS) in anaerobic granular sludges

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Metal binding properties of extracellular polymeric substances extracted from anaerobic granular sludges

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Characterization of the Extracellular Polymeric Substances (EPS) of anaerobic granular sludges by Size Exclusion Chromatography (SEC)

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Effect of pH on Cadmium and Lead binding by Extracellular Polymeric Substances (EPS) extracted from environmental bacterial strains

International audienceThe effects of the extraction procedure of extracellular polymeric substances (EPS) on their proton/metal binding properties were studied. Nine extraction procedures (one control, four physical and four chemical procedures) were applied to four types of anaerobic granular sludges. The binding capacities between the EPS and lead or cadmium were investigated at pH 7 by a polarographic method. The composition of the EPS extracts varied according to the extraction technique and the origin of the sludge. This induced differences in the pKas and the binding sites density of the EPS extracts. The carry-over of the extractant in the samples strongly affects the properties of the EPS from chemical extraction protocols. Lead and cadmium seem to be bound differently with the EPS, a higher binding capacity was observed for Pb2+ than for Cd2+