78    ANAEROBIC SEQUENCING BATCH REACTOR TREATMENT
OF SWINE WASTES
Richard R. Dague, Professor
Surya R. Pidaparti, Graduate Research Assistant
Department of Civil and Construction Engineering
Iowa State University
Ames, Iowa 50011
INTRODUCTION
A significant problem in the major swine producing areas of the the world is environmental
pollution arising from swine farrowing and feeding facilities.
Environmental pollution problems from swine production have two elements. One is the potential
for water pollution arising from the improper land application of the wastes. The other problem is
odors. The noxious odors from decaying swine manure in confinement feeding facilities are notorious
in rural areas. In addition, the environment within confinement feeding buildings where decaying
manure is stored under slotted floors is not a healthy environment for either the workers-or the
animals.1,2
In Iowa, a state that produces one-fourth of some 80 million hogs slaughtered annually in the U.S.,
confinement swine feeding facilities are being prohibited from locating in the state, primarily as a
result of public resistance.3 Although potential water pollution is a problem, the most serious and
obvious concern is odors. Lawsuits arising from environmental problems associated with confinement
swine feeding facilities are becoming common.4
The odors from swine confinement feeding facilities can be almost totally eliminated with application of appropriate anaerobic treatment technology. An "appropriate technology" is the anaerobic
sequencing batch reactor (ASBR), not the old anaerobic digestion process that has been applied to
swine waste treatment in the past. The conventional, completely-mixed and heated, anaerobic digestion process is capital intensive and its efficiency is subject to wide variations due primarily to
temperature swings.
The research results presented in this paper arise from work being conducted on the development of
the ASBR. The ASBR is highly efficient in the retention of biomass within the reactor, thus compensating for reduced temperatures through increased solids retention times (SRTs) while maintaining
short hydraulic retention times (HRTs). The ASBR is capable of achieving equivalent degrees of waste
stabilization independent of temperature differences, as will be shown in this paper.
BACKGROUND REPORTS
In a 1966 paper, Dague, McKinney and Pfeffer reported the results of studies on what was termed
the "anaerobic activated sludge" process.5 A significant observation in that paper was that equivalent
rates of waste conversion to methane could be achieved at either 35°C or 25°C, if higher concentrations of biomass could be held in the reactor at the lower temperature. In essence, process performance could be independent of temperature with proportionate compensation for the reduced metabolic activity through increased microbial population. It was noted that active biomass concentration
would increase automatically as a result of the reduced rate of endogenous respiration of the microorganisms at the lower temperature.5 This makes possible the achievement of equivalent waste conversions to methane independent of temperature. Another significant aspect of this early research was
that anaerobic microorganisms were observed to flocculate much like the biomass in aerobic activated
sludge.5
This previous work,5 part of the doctoral research of Dague,6 was conducted using a simple, soluble
substrate made from glucose, tryptose broth, and castile soap plus mineral nutrients and trace metals.
In a later report, Dague, McKinney and Pfeffer reported the results of research on solids retention in
46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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