Nitrogen Removal From a Concentrated Waste by
Nitrification and Denitrification
T.B.S. PRAKASAM, Senior Research Associate
Y.D. JOO, Research Specialist
E.G. SRINATH, Research Associate
R.C. LOEHR, Professor
Department of Agricultural Engineering
Cornell University
Ithaca, New York 14580
INTRODUCTION
As a result of rapidly changing agricultural practices, large quantities of concentrated
wastes are generated in considerably smaller areas. From both the BOD and nutrient
standpoint, these wastes can be a major source of pollution. The recently published effluent
guidelines for the feedlot industry (1) indicate that technology is available to avoid point
source discharges from confined livestock and poultry operations. The feasible and logical
disposal alternative for these wastes is the land. However, discharge of these wastes on land
without nutrient control may result in ground as well as surface water contamination.
Although several investigators have reported on the nitrogen control procedures involving
nitrification and denitrification of the municipal wastewaters (2), considerably less effort
has been made in understanding the application of such procedures to relatively
concentrated agricultural wastes. A laboratory and pilot plant scale investigation was
undertaken in the Agricultural waste Management Laboratory, Cornell University, to
study the feasibility of a microbial nitrification and denitrification sequence for the removal
of nitrogen from a concentrated poultry wastewater. This paper presents some of the results
obtained in a laboratory study and discusses their application in a pilot plant study using an
oxidation ditch.
MATERIALS
Nitrification Units — Laboratory Studies
Suspensions of feed were made with fresh poultry manure obtained from experimental
poultry farms at Cornell University. Suspensions of the desired strength were made by
blending a known amount of manure with tap water and filtering the suspension through a
single layer of cheesecloth to separate the coarse solids and feathers. The filtered
suspensions were mixed with tap water to obtain the desired concentration.
Plexiglass units equipped with air diffusers were used for continuous flow studies. All
the continuous flow studies were performed at 20 C. The effect of varying solids retention
time (SRT) and loading rates was studied in these units. During these studies no effort was
made to recycle the solids. Poultry manure suspensions of different strengths were made,
stored at 4 C in a stirred reservoir, and pumped to the continuous flow units through a
multichannel pump. Humidified air was sparged into the units to keep the mixed liquor
solids in suspension and to maintain a high .dissolved oxygen level.
Denitrification Units
Laboratory scale experiments were conducted in batch units. Nitrified waste was
bubbled with helium gas to deoxygenate the waste which was transferred under an
atmosphere of helium to small aspirator bottles (560 ml) fitted with a pinch clamp at the
bottom. After the waste was transferred to the bottles, they were sealed with a serum cap.
The mixed liquor was stirred magnetically. Periodically samples were taken by injecting
helium with a hypodermic needle through the serum cap and opening the pinch clamp to
obtain the sample.
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