A simplified analysis of granule behavior in ASBR and UASB reactors treating low-strength synthetic wastewater

Abstract

-This work presents an analysis of the changes observed in granule characteristics of sludge in the treatment of synthetic wastewater at a concentration of about 500 mgCOD/L in batch, fed-batch (ASBR) and continuous (UASB) bench-scale reactors under similar experimental conditions. Physical and microbiological properties of the granules were characterized as average particle size and sedimentation time and by optical and epifluorescence microscopy. Several samples were analyzed in order to identify the morphologies. Granules from sequencing batch and fed-batch reactors, either with or without mechanical mixing, did not undergo any physical or microbiological changes. However, during the experiment granules from the UASB reactor agglomerated due to the formation and accumulation of a viscous material, probably of microbial origin, when operated at low superficial velocities (0.072, 0.10 and 0.19 m/h). When the superficial velocity was increased to 8.0-10.0 m/h by means of liquid-phase recirculation, the granules from the UASB reactor underwent flocculation and the microbiological characteristics changed in such a way that the equilibrium of microbial diversity in the inoculum was not maintained. As a result, the only reactor that maintained efficiency and good solids retention during the assays was the ASBR, showing that there is a correlation between maintenance of microbial diversity and operating mode in the case of anaerobic treatment of lowstrength wastewaters.

Review of Upflow Anaerobic Sludge Blanket Reactor Technology: Effect of Different Parameters and Developments for Domestic Wastewater Treatment

“…These granules are not washed out from the reactor during operation of UASB. The diameter of the granulated sludge particles has been found in the range of 1.0 to 3.0 mm [8,[116][117][118]. The granular suspensions have greater settling velocities (20-80 mh −1 ) as compared to upflow velocities ( up = 0.1-1.0 mh −1 ).…”

A coupling model for EGSB bioreactors: Hydrodynamics and anaerobic digestion processes

“…An existing set of experimental data obtained by Veronez et al [28], Kato et al [29] and Brito and Melo [12], based on the startup and operational performance of EGSB reactors, is used here to adjust and validate the proposed model. By simplicity, the case studies have been named as R1, R2 and R3, respectively.…”

Microscale Investigation of Anaerobic Biogas Production under Various Hydrodynamic Conditions

“…The anaerobic biogas production is gaining attractive interests within this context, and the anaerobic digestion has been considered as one of the most suitable alternatives to produce the biogas, which can be recovered and then converted into heat or electricity as a renewable energy source. , In recent years, anaerobic digestion technology was significantly improved by the development of digesters based on granular sludge. The related study focused mainly on the granulation process, especially, the formation, structure, and metabolism of granular sludge in the anaerobic reactors − or aerobic reactors such as SBR; , other studies were devoted to the dynamical effects of operational or environmental variation on the performance of the anaerobic reactor, such as hydraulic and organic load variation, temperature, nutrients, inhibition, pH, alkalinity, pretreatment. − These works reveal the importance of monitoring various parameters during anaerobic digestion from a point of view of process control. Until now, little is known about the effect of hydrodynamic conditions, e.g.…”