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

Abstract

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 d and 20 kg COD m d. 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 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. 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.

Chitosan for direct bioflocculation of wastewater

“…Apart from raw powdered and flake chitosan, the derivatives of chitosan have also been used to treat palm oil mill effluents. This involves dissolving powdered chitosan with acid solutions (Ahmad et al 2006;Torres et al 2018). In some cases, chitosan is mixed with other oxidative chemicals such as ferric chloride, ferrous sulfate and hydrogen peroxide (Parthasarathy et al 2016;Tadza et al 2016).…”

Divergence of Granular Sludges and Microbial Communities in Two Types of Anaerobic Reactors Treating Different Wastewaters

“…At the genus level (Fig. 5D), Geobacter (13.0%), which can couple ethanol, acetate, formate or lactate oxidation with the reduction of iron or manganese oxides [23], was the most predominant genus among the shared OTUs. Syntrophobacter (2.4%) and Syntrophorhabdus (1.3%) also showed high relative abundances.…”

Influence of support media supplementation to reduce the inhibition of anaerobic digestion by phenol and ammonia: Effect on degradation performances and microbial dynamics

“…A wide variety of inhibitors can induce anaerobic digester disruption [3] . To avoid performance losses, support media such as zeolites [4] , activated carbon [5] or chitosan [6] can be used to mitigate inhibitions. Fig.…”