Ammonia Removal and Recovery From
Fertilizer Complex Wastewaters
DAVID W. ARNOLD, Vice President
Mississippi Chemical Corporation
Yazoo City, Mississippi 39194
WILLIAM E. WOLFRAM, Project Manager
Roy F. Weston, Inc.
West Chester, Pennsylvania 19380
AMMONIA REMOVAL — AMMONIA RECOVERY
The available ammonia removal techniques ultimately either destroy the ammonia by
converting it to nitrogen (breakpoint chlorination or biological nitrification-denitrifica-
tion); concentrating it, ideally to a reusable or saleable ammonia product (ion exchange or
membrane filtration); or stripping it as ammonia gas (air or steam stripping). In
view of present day natural gas allocations and the consequent limited availability of
ammonia, treatment plant designers should be encouraged to search for ammonia removal
techniques which recover, rather than destroy, ammonia. Although each industrial
wastewater offers distinct treatment challenges, the conclusions from this study (recently
conducted for the fertilizer industry) should be of interest to other industries faced with
ammoniacal nitrogen and phosphorus removal requirements.
Roy F. Weston, Inc., in concert with Mississippi Chemical Corporation, conducted a
laboratory-scale treatability study to develop a physical/chemical wastewater treatment
technique for fertilizer complex wastewater to control nitrogen, phosphorus, and fluoride.
The removal technique investigated consisted of precipitation of fluroides,
phosphorus, and silica by lime addition, this being well-known technology in the fertilizer
industry. Second-stage treatment was required for the precipitation of ammonia, using
phosphoric acid and magnesium to produce an insoluble chemical complex of ammonia,
phosphate, and magnesium. Further polishing of the wastewater was necessary to remove
residual phosphate. Ammonia removals of 96 percent were demonstrated by the treatment
process. The insoluble struvite complex produced by the ammonia removal stage is a
potentially saleable grade fertilizer product (5-24-0). Effluent fluoride and phosphorus
values were below 25 mg/l and 2 mg/l, respectively.
RAW WASTEWATER CHARACTERISTICS
The wastewater being considered for treatment was synthesized for treatability testing
from available materials, including the background well water, fluosilicic acid (H2SiF6),
ammonium hydroxide (NH4OH) potash, and fertilizer dust containing phosphate and
potassium. Table I presents the raw wastewater constituents.
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