Section Four
WASTE TREATMENT PROCESSES
C. NITROGEN TRANSFORMATION
42    BIOLOGICAL TREATMENT LIMITATIONS AND PROBLEMS
ASSOCIATED WITH
AMMONIA-NITROGEN COMPLEXATION
Enos L. Stover, President
STOVER & ASSOCIATES, INC.
P.O. Box 2056
Stillwater, Oklahoma 74076
INTRODUCTION
Biological treatment of high strength industrial wastewater can be very complex due to macronutri-
ent and micronutrient deficiency and limitations, especially nitrogen limitation, balancing and complexation problems. The two primary macronutrients of concern are nitrogen and phosphorus. Micro-
nutrients are of lesser concern, but can also create serious operational problems under deficient
conditions. Nitrogen in the form of ammonia-nitrogen is normally the most critical nutrient limiting
growth factor for high strength industrial wastewaters. The nitrogen must exist or be converted to a
free (uncomplexed) state as ammonia-nitrogen to be available for use in biological synthesis reactions.
The various competing mechanisms of nitrogen chemistry can seriously complicate the biological
treatment of high strength wastewaters.
Highly variable high strength nitrogen deficient wastewaters can create very difficult operational
challenges due to the nitrogen balancing act. Ammonia-nitrogen complexation can occur, such that
even with the addition of excess ammonia-nitrogen above synthesis requirements, serious operational
problems occur. Excess ammonia-nitrogen can also be nitrified to nitrite-nitrogen and nitrate-nitrogen
which are not readily available for biological synthesis reactions. These oxidized forms of nitrogen
have to be reduced back to ammonia-nitrogen before the nitrogen can be used for synthesis reactions.
Serious problems from nitrogen deficiency can consist of filamentous and nonfilamentous bulking
sludge, formation of extracellular polysaccharide, limited biochemical reaction rates, and deteriorated effluent quality.1 The complexation reactions are catalyzed by certain environmental
conditions.
An apparent incident of ammonia-nitrogen deficiency problems due to ammonia-nitrogen complexation reactions was reported by Deeny, et al.2 Even though excess ammonia-nitrogen was available in the wastewater, the biological conditions in the treatment plant exhibited ammonia-nitrogen
deficiency symptoms of poor settling bulking sludge and encapsulated organisms. All the symptoms
and problems were resolved by adding excess free uncomplexed ammonia-nitrogen to the wastewater.
It was postulated that the ammonia-nitrogen was complexed in some form of a ferrous ammonium
sulfate complex which could not be readily utilized for biological synthesis reactions. The authors
have also observed these types of symptoms and problems numerous times at various treatment
plants. A case study is presented of a study performed to demonstrate that serious ammonia-nitrogen
complexation reactions can occur in the presence of excess ammonia-nitrogen being added to the
wastewater.
EXPERIMENTAL PROGRAM
This ammonia-nitrogen complexation study was performed with a continuous flow aerobic activated sludge reactor. The aerobic activated sludge reactor was an internal recycle system made of
plexiglass with a 3.0-L aeration/mixing zone and a 1.5-L settling/clarification zone. Mixing and
oxygen supply in the reactor were accomplished with diffused aeration. The aerobic reactor was
47th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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