EFFECT OF TOXICANTS ON BIOLOGICAL NITRIFICATION FOR
TREATMENT OF FERTILIZER INDUSTRY WASTEWATER
Shafkat A. Beg, Associate Professor
Rashid H. Siddiqi, Associate Professor
Shamsuddin Ilias, Research Assistant
University of Petroleum and Minerals
Dhahran, Saudi Arabia
The fertilizer industry presently ranks as one of the largest industries in the world. Global
usage of various types of chemical fertilizers in 1951 was estimated at 17.4 mdlion tons, 70
million tons in 1971 and is to reach 115 mdlion tons by 1980 [ 1 ]. Current annual usage of
more than 32 mdlion tons of chemical nitrogenous fertilizer alone is approaching the order
of total nitrogen fixed biologically [2].
A fertilizer industry produces mainly either the nitrogenous or the phosphatic fertilizers.
Some produce both and also the complex fertilizers such as ammonium sulphate and the
diammonium phosphate [3,4]. It is difficult to define the volumes and the compositions of
various wastewater streams from a fertilizer plant because of variations in the manufacturing
process and the operational phdosophies of different plants. In addition, a large fraction of
the total waste discharges is due to the process spills, which are extrememly irregular in
frequency and size (5). An overview of the concentrations of the different nitrogen contaminants in the process waste streams from the nitrogenous fertilizer plants in the U.S.
is shown in Table I [6]. Further, the wastes produced are related to the type of fertdizer
being manufactured. Table II shows the characteristics of process effluents from various
sections of a typical complex fertilizer plant [3].
The wastewaters from nitrogen fertilizer industry containing large concentrations of
nitrogen in the form of ammonia and urea can be detrimental to the quality of receiving
waters. There are several means of removing nitrogen from wastewaters which include
ammonia stripping, ion exchange, breakpoint chlorination and biological nitrification-
denitrification [7]. In the nitrification-denitrification process ammonium-nitrogen (NH4- N)
is first oxidized to nitrate by autotrophic bacteria in an aerobic reactor and then reduced
to nitrogen gas by a variety of facultative heterotrophic bacteria in a second reactor in an
anoxic environment according to the following reactions [2,8].
Nitrification:
Denitrification:
NH4+202    Nitrifiers 2H* + H20 + N03
NO3 + I CH3OH Denitrifiers \-N2 + |- C02  +5- HjO + OH"
(1)
(2)
Table I. Nitrogen Compounds in Process Waste Streams and Wastewater Volume from Nitrogen
Fertilizer Plants in the U. S. [6]
Contaminant
NH3
Plant
NH4NO3
Plant
(NH4)2S04
Plant
Urea
Plant
NH3(mg/l) 20-100                200-2,000 10-10,000          200-4,000
N05(Mg/l) 50-1,000
Urea (mg/1) 50-1,000
Volume (Uter/ton of product) 400-4,000              200-4,500 400^*0,000         800-15,000
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