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THE EFFECT OF PIG DIET AND SOLID/LIQUID SEPARATION OF PIG SLURRY ON PHOSPHORUS FRACTIONATION
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Pp. 463-471 in the Ninth International Animal, Agricultural and Food Processing Wastes Proceedings of the 12-15 October 2003 Symposium (Research Triangle Park, North Carolina USA), Publication Date 12 October 2003. 701P1203.(doi:10.13031/2013.15284)
Authors: M-L. Daumer, F. Béline, M.Spérandio
Keywords: animal wastes, phosphorus recycling, biological treatment, characterization, liquid manure, magnesium, calcium
In some intensive animal production areas, the accumulation of nutrient surpluses (N, P,) from
livestock effluents has led to severe pollution problems (water, air, soil).
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The control of this potential pollutant load requires the development of processing methods to
remove the excess nutrients. In France, biological treatment based on aeration
(nitrification/denitrification) is the most widespread technology on farms. Nowadays this
treatment has to be adapted to include phosphorus removal as well as nitrogen removal.
For this purpose, the characteristics of pig slurry from different farms (with or without phytase in
pig diets) were studied through phosphorus, magnesium and calcium fractionation including
ortho-P, organic dissolved P, precipitated P, biomass-P and residual-P. Moreover, the influence of
mechanical separation (press-auger and centrifugation) was studied.
In raw slurry, 4-10 % of phosphorus was soluble, 60-85% was precipitated and 3-20% was
phosphorus linked to the biomass. The total phosphorus concentration is slightly decreased when
diets with phytase are used (12%). Without phytase, around 20% of total phosphorus was
residual, i.e. on a very insoluble form, probably as calcium phytate. Up to 50% of this form
remained after the separation step. No residual phosphorus was found with phytase in the diet.
Both separators studied (press auger and centrifugation) did not affect the concentration of soluble
compounds in the separated slurry. When TSS concentration in raw slurry is high (>3,5%), the
abatement of the TSS concentration is similar with centrifugation or press-auger. In contrast,
centrifugation and press-auger decreased the total phosphorus concentration in the effluent by up
to 50% and 15% respectively. Most of the phosphorus removed by centrifugation is precipitated
The difference between the amount and the quality of the phosphorus present in the effluents for
each type separator should be considered in proposing a relevant dephosphorisation strategy for