NITRIFICATION OF COKE OVEN WASTEWATER
WITH HIGH AMMONIA CONCENTRATION
Meint Olthof, Manager
Industrial Waste Section
Duncan, Lagnese, and Associates, Inc.
Pittsburgh, Pennsylvania 15237
INTRODUCTION
Several industrial processes result in wastewaters with high ammonia concentrations.
Almost without exception each of these industrial categories will be required to drastically
reduce the ammonia concentration before the wastewater can be discharged to surface
waters. Alternatives available to reduce the ammonium discharge are:
1. Recovery by in-plant process modifications
2. Air stripping
3. Biological nitrification
4. Selective ion exchange
5. Breakpoint chlorination
For plants generating high ammonia containing wastestreams only the first three alternatives are practical. Selective ion exchange will result in frequent regeneration and high chemical cost and breakpoint chlorination requires large quantities of chlorine gas and can produce
undesired side reactions. In-plant process modifications resulting in a recovered high ammonia containing product is the ideal way of eliminating or alleviating a waste disposal problem.
However, several factors could decide against this alternative:
1. The recovery technology is not well developed
2. No ready markets are available for the recovered product
3. Incorporating required process modifications might not be practical.
Air stripping at elevated pH will reduce the ammonia concentration rapidly but it transfers a water pollution problem to an air pollution problem. Also the chemical requirement
for reducing the ammonia concentration to low levels is high. Therefore air stripping is
probably attractive as a pretreatment step to reduce the bulk of the ammonium as long as
this practice is considered environmentally acceptable in the particular geographical area.
Biological nitrification is the alternative that will be discussed in detail in this paper. Provided that high enough oxidation rates can be obtained this alternative can be attractive
since the biological process is relatively simple. A disadvantage is that the end product is
nitrate that in turn is regulated for drinking water supplies. Depending on the locality it
could therefore become necessary to add a denitrification step.
This paper will present results on nitrification experiments with coke oven wastewater
containing ammonia concentration varying from 100 to 1000 mg/1. Because of the high
nitrate concentrations produced also denitrification rates were determined as a function of
the concentration of organic material.
BACKGROUND INFORMATION
Nitrification
Biological nitrification is the result of activities of two types of bacteria. The first stage
is the oxidation of ammonia to nitrite by a bacteria group called Nitrosomonas. The nitrite
is further oxidized to nitrate by the Nitrobacter. Both types of bacteria are autotroph which
means that only inorganic compounds are required to satisfy the food supplies. Carbonate is
used as a carbon source, while the oxidation of ammonia to nitrite (for nitrosomonas) or of
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