Modeling the liquid flow in up‐flow anaerobic sludge blanket reactors

Abstract

By means of stimulus-response experiments an Li(+) tracer, models for the fluid flow in a 30-m(3) UASB reactor, used for the anaerobic treatment of wastewater, were tested. From the model with the best fit it could be derived that both the sludge bed and the sludge blanket can be described as perfectly mixed tank reactors with short-circuiting flows; the settler volume acts like a plug-flow region.Apart from the volumes of the different flow regions, two parameters are necessary and sufficient to describe the fluid flow in a well functioning UASB reactor, i.e., the short-circuiting flow over the sludge bed and the short-circuiting flow over the sludge blanket. The volumes could be measured accurately.The short-circuiting flow over the sludge bed is a linear function of the sludge bed height. When the optimal height of the sludge bed is defined as the height for which the short-circuiting flows are as small as possible, a bed-height of 3.5-4 m is sufficient (for superficial gas velocities between 1 and 1.5 m/h). This is in contradiction to the results of other authors. The short-circuiting flows over the sludge bed and the sludge blanket were also influenced by the superficial gas velocity.

Dispersed plug flow model for upflow anaerobic sludge bed reactors with focus on granular sludge dynamics

“…1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,17,18,19,20,21,22,23,24,25,26,27,28,29), based on the combination of sludge dynamics and bacterial metabolism. To our knowledge, this is the first successful attempt in the creation of models of a new generation that are able to simulate complex space heterogeneous dynamics, not only of solutes but also of the granular sludge (e.g.…”

“…immanent formation and development of sludge bed and blanket zones, sludge wash-out) inside UASB reactors. The second principal difference of the presented model with previously proposed models of UASB reactors [3,36] is that it provides a universal description of both hydrodynamics and solids dynamics by continuous equations throughout the reactor volume. The third prominent feature of the dispersed plug flow model is that it relies solely on internal mechanisms of the bioprocesses to predict sludge washout from the reactor.…”

“…Each of these compartments is assumed to have ideal attributes (such as ideal mixing or plug flow), and they are linked with each other by bypassing and back mixing flows [3,10,11,36]. These multi-compartment models are generally capable of fitting experimental data quite satisfactorily for UASB reactors operating under steady-state conditions.…”

Helminth Egg Removal Capacity of UASB Reactors under Subtropical Conditions

“…Likely, the better retention might be associated to the absence of biogas production and thus turbulence. Therefore, in the absence of turbulence, the wastewater flow is more homogeneous [65][66][67][68], and helminth eggs settling follow a discrete settling pattern. Another remarkable observation is that even at the lowest upflow velocity (0.09 m·h ) helminth eggs do not settle completely nor are retained completely by the sludge bed.…”

Development of monitoring and control technology based on trace gas monitoring. Final report

“…In treating cane sugar wastewater, it was observed that at low organic loading rates, adequate mixing of an U4SB reactor contents did not take place (Manjunath et ai.. 1989). Bolle et al (1986) developed a model in which both sludge bed and sludge blanket can be described as completeIy mixed flow reactors with short-circuiting flow paths, while the settler volume was best described as a plug flow reactor. Short-circuiting flow through the sludge bed was a function of the bed height.…”