Effect of mixing mode on the behavior of an ASBBR with immobilized biomass in the treatment of cheese whey

Abstract

-A hydrodynamic study of a mechanically stirred anaerobic sequencing batch biofilm reactor (ASBBR) containing immobilized biomass on polyurethane foam was performed with the aim to determine homogeneity of the reactor based on total mixing time. Turbine or helix propellers were used for stirring at rotor speeds of 100, 200, 300 and 500 rpm. Experimental values obtained were fitted to a Boltzmann sigmoid. Homogenization times of the reactor were negligible when compared to the 8-h cycle time for all conditions studied. At low propeller rotations the turbine propeller showed the best performance. For higher rotations total mixing times were similar for both propellers; however the helix propeller had better homogeneity conditions. At a subsequent stage the system was operated in batch mode treating cheese whey at concentrations of 500, 1000 and 2000 mgCOD/L and rotations of 200, 300 and 500 rpm. In these assays the importance of the propeller became evident not only for mixing, but also for substrate flow across the bed containing immobilized biomass. Due to axial flow, the helix propeller offered better mass transfer conditions, evidenced by improved organic matter conversion and lower production of total volatile acids.

ASBR Applied to the Treatment of Biodiesel Production Effluent: Effect of Organic Load and Fill Time on Performance and Methane Production

“…Many works are encountered in the literature on the influence of different process variables, which have as main objective the qualitative and quantitative knowledge of the relationship between these variables and efficiency and stability to optimize the system [4][5][6]. Studies on the influence of stirring, which is related to the mass transfer resistance from the liquid phase to biomass, affecting the global reaction rate, have been dealt with in a number of papers, whether by implementing liquid phase recirculation [7] or mechanical stirring [8][9][10][11][12]. Fill time is another important variable that has been investigated, and may influence process performance by the bioavailability of the substrate contained in the wastewater, by inhibition or toxicity of effluents with high organic load or lacking nutrients and/or alkalinity [13][14][15].…”

Effect of impeller type and stirring frequency on the behavior of an AnSBBR in the treatment of low-strength wastewater

“…Pinho et al (2004) showed that stirring in sequencing batch reactors, in addition to promoting mixing in the reactor, increases solid-phase mass transfer and the solubilization of particulate organic matter. Damasceno et al (2008) and Michelan et al (2009) both noted that improvement in homogenization, liquid flow and solid-liquid mass transfer were directly related to the type of impeller used.…”

Effect of Organic Load on the Performance and Methane Production of an AnSBBR Treating Effluent from Biodiesel Production

“…Investigation on the effect of agitation, which is related to mass transfer resistance of the liquid phase to the biomass, has been dealt with in some works, accomplished either by recirculation of the liquid phase [6,7,25] or by mechanical stirring [1,12,17,27,28]. Fill time or feed strategy is another important variable that has been investigated and which may affect process performance by the availability of the substrate in the wastewater, by inhibition or toxicity of effluents containing high organic load or lacking nutrients and/or alkalinity [2,4,23].…”