PILOT PLANT STUDY OF AN ANAEROBIC FILTER FOR TREATING
WASTES FROM A COMPLEX SLAUGHTERHOUSE
Dewey R. Andersen, Professor
Lanny A. Schmid, Graduate Student
Department of Civil Engineering
University of Nebraska — Lincoln
Lincoln, Nebraska 68588
INTRODUCTION
Decentralization of the meat packing industry and the resultant location of many facilities in rural
areas near the source of supply has necessitated that many plants provide their own waste treatment
facilities. Following pretreatment to recover saleable by-products, a common treatment system consists of anaerobic-aerobic biological systems operated in series. Traditionally anaerobic lagoons have
been popular and continue to constitute an economical, simple method of reducing the waste strength
prior to aerobic treatment processes. However, odor problems have been encountered at some facilities and increased energy costs have stimulated interest in recovery and use of the methane gas
produced in the anaerobic process. As a result, some anaerobic lagoons have been covered.
Additional modifications have been considered to increase the organic loading capacity of the
anaerobic system and to provide greater stability to the process. These modifications serve to increase
the concentration of microorganisms within the system by enhanced retention and/or return of microbial solids from the effluent and reduce short circuiting. In this study, a pilot-plant scale, upflow
anaerobic filter was evaluated for treatment of wastewaters from a complex slaughterhouse.
PILOT PLANT STUDY
The anaerobic filter used in this study was located in the inedible, rendering area of a complex
beef slaughterhouse. The unit consisted of a fiberglas tank 1.5 m (5 ft) in diameter and 4.9 m (16
ft) in height. The tank was divided into three functional zones. The lower zone, which had a height
of 1.1 m (3.5 ft), included the influent port and a sludge withdrawal or sampling port. A dispersion
ring located directly above this zone served to distribute the influent uniformly across the tank and
support the filter media which was randomly placed to a depth of 3.3 m (11 ft) above the dispersion
ring. The filter media used, Norton Actifil 90, consisted of plastic cylinders 90 mm (3.5 in.) in diameter and 90 mm (3.5 in.) in height. The remaining space at the top of the tank, 0.5 m (1.5 ft)
contained a gas vent and effluent port and served for scum and gas storage. As indicated in Figure
1, the unit was also provided with eleven additional sampling ports located at various heights in the
filter.
During start-up the filter unit was seeded with sludge from the anaerobic lagoon system serving
the slaughterhouse. During this period, the feed solution consisted of a diluted mixture of stick water,
a waste stream from the coagulation of blood with steam, and blood/fat bearing waste. The proportion of blood/fat bearing waste and organic loading on the unit was gradually increased during
the acclimation period.
Initially the effluent from the dissolved air flotation (DAF) unit was used as feed for the anaerobic
filter. However, increased plant production and resultant overloading and reduced grease removal
efficiency in the DAF unit necessitated additional pretreatment. A 6000 1 (1600 gal) stainless steel
settling tank and a 1900 1 (500 gal), open top, fiberglass mixing tank were added in series ahead of
the filter feed pump. Grease and settled solids were removed manually from the settling tank on a
daily basis. The mix tank, which was provided with a 0.75 horsepower mixer, was filled from the
settling tank by a float controlled transfer pump.
Filter loadings were determined from analyses of the effluent from the mix tank. The feed pump
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