Section Three.
WASTE TREATMENT PROCESS
C. ANAEROBIC PROCESSES
71 COMPARISON OF THE NOVEL MULTIPLATE ANAEROBIC
REACTOR WITH THE UPFLOW ANAEROBIC SLUDGE
BLANKET REACTOR
R. El-Mamouni, Graduate Student,
D. Rouleau, Professor,
R. Mayer, Professor
Dept. Chemical Engineering
Ecole Polytechnique
Montreal, Canada H3C 3A7
S. R. Guiot, Research Officer,
R. Samson, Section Head
N.R.C., Biotechnology Research Institute
Montreal, Canada, H4P 2R2
INTRODUCTION
The need for more cost-effective treatment of liquid wastes of various strength has led to renewed
interest in anaerobic digestion and development of a new generation of bioreactors.1 These advanced
designs permit an important reduction of the hydraulic retention time (HRT) and of the working
reactor volume, with a concommitant improvement of the solid retention time (SRT).
The effectiveness of any anaerobic bioreactor is essentially based on the amount of the biomass that
can be retained in the reactor, the specific activity of that biomass and the degree of the contact that
can be established between the biomass and the substrate. As these objectives are encountered, a large
organic loading rate (OLR) can be applied and high strength wastewater can be treated. The most
popular anaerobic bioreactor capable of retaining a large amount of biomass is the Upflow Anaerobic
Sludge Bed reactor (UASB). The UASB concept2 has a number of advantages over other advanced
anaerobic bioreactors, namely its ability to retain more active biomass in the reactor and to avoid
plugging and short-circuiting, problems that are common with the anaerobic filter and the down flow
stationary fixed film reactors.
Nevertheless, a serious drawback of the UASB reactor is the possibility of excessive bed expansion
and loss of biomass with the effluent. This process also requires well settling granular sludge, which is
sometimes difficult to obtain. For this reason, compartmentation was introduced in some anaerobic
reactor designs.3 In the Baffled Reactor (BR), the waste flows horizontally and around baffles and
passes through an inverted siphon to separate the gas from the liquid. The BR has been shown to
handle organic loads among 3 and 7 kg chemical oxygen demand (COD)/m3.d with a COD removal
efficiency of about 78%. Thereafter, in the BT modified version (MBR),3 the downflow chambers
were narrowed, the lower edges of the baffles were slanted to route the flow to the center of the
upflow chambers and the effluent was recycled back into the reactor. The MBR showed a COD
removal efficiency of 82% at an organic load of 8 kg COD/m3.d. However, these reactors suffered
from short-circuiting and clogging.
The design of the novel MPAR was developed at Ecole Polytechnique of Montreal and first used
for bioconversion of the biosulfite pulping liquor to ethanol.4 The novel MPAR consists of three
superimposed compartments separated by plates taped with several apertures covered by bubble caps.
The liquid was thus allowed to flow upwards from one compartment to the next, while about 50% of
46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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