Research Anaerobic Migrating Blanket Reactor
After performing a parallel study with upflow anaerobic sludge blanket (UASB) and anaerobic sequencing batch reactor (ASBR) processes, problems observed with these two systems were addressed by developing a novel reactor. A detailed description of this reactor, the anaerobic migrating blanket reactor (AMBR) is presented below. The process was patented in 1999 (PDF of US Patent No. 5,885,460) and described in a Water Research article (PDF of AMBR development paper).
The AMBR is a continuously fed, compartmentalized reactor without the requirement of elaborate gas-solids-separation and feed-distribution systems (Fig. 1). Effluent recycling is not necessary, but gentle intermittent mixing is needed to maintain sufficient contact between biomass and substrate due to the absence of an upflow hydraulic pattern. The influent flows horizontally into one end of the reactor and the effluent leaves from the other end. Consequently, the final compartment receives the lowest substrate concentration, and therefore the substrate utilization rate of the microbes in this compartment is low. This results in low biogas production, which enables the final compartment to serve as an internal clarifier preventing biomass loss in the effluent. Due to the flow pattern and the observed biomass migration, biomass accumulates in the final compartment. To prevent excessive accumulation of biomass in this compartment, the flow needs to be reversed periodically. Thus, after reversing the flow, the final compartment becomes the initial compartment and the earlier initial compartment serves as the internal clarifier (final compartment). To prevent a break-through of substrate when the flow is reversed, at least three compartments are required in a continuously-fed AMBR. The influent is fed for a short period of time into the middle compartment before the flow is reversed.
Fig. 2 shows a full-scale AMBR in Costa Rica (designed to treat 0.26 million gallon per day of an ice-cream factory).
Fig. 1. Schematic of a 3-compartment AMBR.
Fig. 2. Picture of a full-scale AMBR in Costa Rica.