ANAEROBIC FLUIDIZED BED WHEY TREATMENT
Paul H. Boening, Visiting Assistant Professor
Department of Civil Engineering
State University of New York at Buffalo
Buffalo, New York 14260
Vadar F. Larsen, Professor
Department of Biotechnology
Massey University
Palmerston North, New Zealand
Anaerobic processes have several advantages over aerobic processes for waste treatment.
The main advantage is that anaerobic processes are energy producing, while aerobic processes
are energy consuming. Anaerobic processes also have the advantage of producing lower quantities of biological solids for final disposal. The major disadvantage of anaerobic processes
has been the longer hydraulic retention time required for treatment.
Fixed film reactors offer a solution to the problem of long hydraulic retention times and
avoid the solids separation problems associated with the anaerobic contact process. Anaerobic filters have been extensively studied after the initial work by Young and McCarty
[ 1 ] and have been modified to give the characteristics of a completely mixed system by De-
Walle and Chian [2).
Fluidized reactors have been evaluated both for aerobic and denitrification processes
[3,4] and anaerobic processes [5]. This type of reactor offers advantages over other fixed
film reactors. Fluidized bed reactors have much larger specific surface areas which allows increased concentrations of microorganisms. Larger specific surface area allows shorter
hydraulic retention time for the same amount of treatment or it allows the use of lower
operating temperatures.
Specific surface areas of 80 m2/m3 have been reported for trickling filters and 160
m2/m3 for rotating biological contactors [61. A specific surface area of 206 m2/m3 has
been reported for an anaerobic filter [2] while a specific surface area of 3000 m*/m3 has
been reported for a fluidized bed reactor [3]. Concentrations of microorganism of 40 g/1
are possible in denitrification processes [6) and over 30 g/1 have been measured in anaerobic
processes [5].
Packed bed reactors such as anaerobic filters often experience problems of increased pressure
drop due to the accumulation of biomass. To prevent plugging relatively large voidage must
be maintained which limits specific surface area and biomass concentration. Fluidized bed
reactors overcome these problems allowing the use of low-voidage, high-surface-area media
[7]. Also, influent suspended solids are not a problem and bed material may be easily added
or removed. Tapered beds offer the additional advantage of greater stability over a large
range of flowrates [8J.
Previous anaerobic work with fluidized bed reactors was performed on dilute waste of
COD values up to 600 mg/l. Waste stabilization efficiency up to 80% was obtained at a 3
hour hydraulic detention time [5]. This chapter presents work conducted to demonstrate
the potential of and evaluate kinetic coefficients, for anaerobic fluidized bed treatment of
moderately strong whey wastes of 2000-7000 mg/l COD.
MATERIALS AND METHODS
Two fluidized bed reactors were used in this work. Reactor number one (Figure 1)
was a tapered  bed  with a 0.095-m  diameter at the top and an inlet diameter of 3.2 x
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