Development of a new high-rate anaerobic process for the treatment of industrial and domestic wastewaters: the anaerobic migrating blanket reactor (AMBR)

Abstract

<p>The anaerobic migrating blanket reactor (AMBR) was developed as a new high-rate system for the treatment of industrial and domestic wastewaters, at Iowa State University. The AMBR, a continuously fed, compartmentalized reactor, required mechanical mixing to obtain a sufficient biomass/substrate contact. The formation of granular biomass was not dependent on a hydraulic upflow pattern in the reactor, but was dependent on biomass migration over the horizontal plane of the reactor and the settling characteristics of the final compartment. To prevent acclimation of biomass in the final compartment, the flow was reversed in a horizontal matter. Keeping the pH sufficiently high in the initial compartment without recycling effluent was another advantage of reversing the flow. This also prevented total phase separation of acidogenesis and methanogenesis in the AMBR;Laboratory-scale AMBR systems have achieved high organic removal efficiencies when fed with non-acidified sucrose as a substrate at chemical oxygen demand (COD) loading rates up to 30 g/L/d. Furthermore, the AMBR was able to retain high levels of granular biomass at these loading rates. Due to moderate shear forces by mechanical mixing, the laboratory-scale AMBR was able to treat non-acidified sucrose at food to microorganism (FIM) ratios higher than found for other high rate systems. The AMBR out-competed the upflow anaerobic sludge blanket (UASB) and anaerobic sequencing batch reactor (ASBR) in a laboratory-scale comparison in terms of reactor performances and maximum organic loading rates;A mature granular blanket was formed after four months of operating a 54-liter AMBR, seeded with flocculent primary digester sludge. This was accomplished with moderate hydraulic selection pressures at the start of the run, in which reactor performances were sufficient to build up an active biomass, without losing the selection mechanism for better settling biomass;A 20-liter AMBR was able to effectively remove organic material from dilute non-fat dry milk (NFDM) solution at a concentration of 600 mg/L under psychrophilic conditions. Moreover, this reactor was able to retain its granular biomass after the hydraulic retention time (HRT) was decreased from four to one hour during hydraulic shock load studies. Finally, staging or partial phase separation was found in the AMBR in which relatively more methanogens were present in the inside compartments.</p>