29    INITIAL STUDIES ON THE ANAEROBIC
MIGRATING BLANKET REACTOR
Largus T. Angenent, Graduate Research Assistant
Richard R. Dague, Professor of Environmental Engineering
Department of Civil and Construction Engineering
Iowa State University
Ames, Iowa 50011
INTRODUCTION
The anaerobic migrating blanket reactor (AMBR) is a new high-rate process for the treatment
of industrial and municipal wastewater being developed by the writers and coworkers at Iowa
State University, Ames, Iowa, USA. The AMBR is a continuously fed compartmentalized system
that reverses its flow in a horizontal manner. This new process combines the advantages of an
anaerobic sequencing batch reactor (ASBR) with that of a continuously fed process. The ASBR
was developed in the same laboratory as the AMBR. A U.S. Patent (No. 5,185,079) for the
ASBR was issued to the Iowa State University Research Foundation in May 1993.
The purpose of this chapter is to present the performance of a 12-liter AMBR. These results
will be compared with the performances of a 12-liter ASBR and a 12-liter UASB reactor that
was presented previously.1 Some results of a 54-liter AMBR that was operated at the same loading conditions will also be presented. Further, the fundamental principles, characteristics, and advantages of the AMBR will be discussed.
REQUIRED CONDITIONS
Wirtz and Dague2 found granules in an ASBR in five months after seeding the reactor with
nongranular anaerobic sludge. This indicates that granulation does not depend on a hydraulic upflow pattern, which was also found by Vanderhaegen et al} With this knowledge, new reactor
technology, like the AMBR process, can be developed. In order to successfully create a new
high-rate immobilized biomass reactor to provide an anaerobic treatment process which can handle high organic and hydraulic loading rates, the following conditions should be met. Research
showed these six conditions are satisfied for the ASBR process, whenever the batch fed system
is operated in a way that promotes granulation.14-5 The six conditions are:
Selection of a Granular Biomass
The selection for granular biomass is a condition that should be met in order to handle high
volumetric loading rates. Granulation results in a better settleability of the biomass, which increases the retention of the biomass. Another advantage of granular biomass over flocculent biomass is a higher specific methanogenic activity, possibly due to favourable conditions for the
methanogens inside the granules.6"' The formation of a granular blanket over time occurs due to
a selection process of the biomass after growth nuclei are present. The selection process consists
of poorly settling biomass washing out of the reactor and the heavier, more rapidly settling, aggregates being maintained in the reactor.
High Retention of Biomass
High levels of biomass are a requirement for a high loading potential of anaerobic processes.
The process loading, based on food to microorganism (F/M) ratio, should be low to achieve effi-
51st Purdue Industrial Waste Conference Proceedings, 1996, Ann Arbor Press, Inc., Chelsea, Michigan 48118.
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