49    PERMANENT INCREASE OF THE PROCESS
TEMPERATURE OF MESOPHILIC UPFLOW
ANAEROBIC SLUDGE BED (UASB) REACTORS TO
46, 55, 64 AND 75°C
Jules B. van Lier, Doctoral Candidate
Gatze Lettinga, Professor
Department of Environmental Technology,
Wageningen Agricultural University,
The Netherlands
Alberto J.L. Macario, Senior Scientist
Everly Conway de Macario, Senior Scientist
Wadsworth Center for Laboratories and Research,
New York State Department of Health and
School of Public Health,
State University of New York at Albany,
Albany, New York 12201-0509
INTRODUCTION
Anaerobic digestion is a commonly used technology for the treatment of biodegradable waste
streams. The application possibilities are intensively researched in the last 20 years. Nowadays several
types of waste waters are treated which were previously believed not to be suitable for this technology.
Also reactor conditions are getting more advanced, especially after the introduction of anaerobic 'high
rate' systems with a high solid retention time. The Upflow Anaerobic Sludge Blanket (UASB) reactor'
is one of the most successful anaerobic 'high rate' reactors developed. The volume in use of full scale
UASB reactors is increasing every year.2
Application of anaerobic digestion under thermophilic conditions was found to be an attractive
alternative, especially for the treatment of hot and concentrated biodegradable waste waters.3,4 Very
high loading potentials with good treatment efficiencies are reported in various studies.5,6 However,
so far only a limited number of full-scale thermophilic reactors are in operation. Furthermore, no
reports mention the application of thermophilic 'high rate' systems at large scale. The main reasons
for this discrepancy are (1) in comparison to the mesophilic digestion process only little research is
carried out in this field; (2) prelimenary research performed in conventional mixed systems demonstrated a higher sensitivity of the process;7 and (3) a reluctant attitude of industries towards any new
technology.
However, with respect to its loading potentials, a thermophilic anaerobic (pre)treatment unit might
reduce substantially the price of an integrated treatment process, especially in areas where space is a
limiting factor e.g., in The Netherlands.
The start-up period was previously seen as the most difficult step of implementation of a thermophilic process. However, recently several start-up strategies are discussed by various authors.3,5,8
From these studies it is clear that a thermophilic start-up is similar to a mesophilic using unadapted
seed material. In this paper we discuss the possibility to switch from a mesophilic UASB process to a
thermophilic, simply, by increasing the process temperature to high levels. In order to determine
possible and optimal temperatures 4 different process temperatures between 45° and 75°C are evaluated. In one of the reactors the effect of moderate temperature fluctuations until 42°C was estimated
on the mesophilic degradation of VFA mixtures, prior to a permanent increase to 46°C. The response
of the VFA degradation on the temperature increase in each reactor is closely followed.
The reactors were fed with a VFA mixture and inoculated with mesophilic granular sludge, a sludge
type commonly found in full scale UASB reactors. Application of mesophilic granular sludge might
47th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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