29    EFFECTS OF BIOAUGMENTATION ON
NITRIFICATION BIOKINETICS
Stan A. Zachopoulos, Process Engineering Specialist
Havens and Emerson, Inc.
Cleveland, Ohio 44114
Yung-Tse Hung, Professor
Department of Civil Engineering
Cleveland State University
Cleveland, Ohio 44115
INTRODUCTION
As the effluent permit requirements become more stringent, higher degrees of wastewater treatment
are required. Industrial and municipal effluents must be very low in ammonia-nitrogen concentrations in order to be allowed for discharge. The most effective and economic method of treatment for
ammonia removal at the concentrations commonly found in municipal and industrial wastewaters is
by biological means.
Biological oxidation of ammonia first to nitrite (N02) and subsequently to nitrate (N03), referred
to as nitrification, is accomplished mainly by the action of two aerobic autotrophic bacterial species,
Nitrosomonas and Nitrobacter. The nitrifying microorganisms exhibit a much slower growth rate
than that of the heterotrophic microorganisms and are more sensitive to environmental conditions
such as temperatures, pH and dissolved oxygen concentrations. In order to achieve the desired levels
of nitrification, wastewater treatment facilities have to provide longer hydraulic and solids residence
times or, in the case of high organic strength wastes, a separate nitrification stage following the
organic removal stage.
In order to increase the organic matter and ammonia removal, many wastewater treatment facilities
supplement specific bacterial strains to the biological system. This bacterial supplementation is
referred to as bioaugmentation. Although many applications of a bioaugmentation have been
reported with mixed results, there has been no single comprehensive study regarding the effects of
bioaugmentation on the nitrification performance of wastewater treatment systems and the kinetic
parameters of the process.
The objectives of this study were to examine the effects of bioaugmentation with heterotrophic and
nitrifying microorganisms on the nitrification process in a combined carbon oxidation-nitrification
aerobic suspended growth biological system under various operating conditions in terms of aeration
time, sludge age and organic strength in the influent; to develop nitrogen removal kinetic rates; and to
examine the effects of bioaugmentation on the nitrogen removal rates under the applied operating
conditions.
EXPERIMENTAL PROCEDURES
Two identical bench-scale reactor systems, each with three continuous flow aerated reactors, were
operated in parallel for a 30-month period. One system was operated as a control and the second was
bioaugmented with a daily dose of 10 mg/L of a commercial bacterial product. The bacterial product
was preserved in a liquid suspension and, according to the manufacturer, contained heterotrophic
microorganisms along with the nitrifiers Nitrobacter and Nitrosomonas.
Primary effluents from municipal wastewater treatment plants were used as a feed in this study.
Since the strength of this water was relatively weak, sodium acetate and glucose were added as an
organic matter source to the raw sewage for certain reactor runs. Ammonium chloride and potassium
biphosphate were also added to provide nitrogen and phosphorus nutrients for the microorganisms.
The chemical doses were added to maintain a BOD:N:P ratio of 100:5:1.
45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.