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Advisor(s)
Abstract(s)
Solid-liquid separation of slurry is used to obtain a solid (SF) and liquid fraction (LF), both
used as organic fertilisers. Previous works showed that the separation technique used
influences the composition of the resulting SF but no data are available relative to the LF.
Four commonly used separation processes were considered e centrifugation, sieving,
enhanced settling by the addition of cationic polyacrylamide (PAM-), and sediment settling
as well as a recent sequential process e sieving followed by PAM addition to the resulting
LF. The resulting LFs and SFs were comprehensively characterised and the amount of N
potentially available for plants after incorporation to soil was also evaluated. Except for
slurry that was only sieved which was very similar in composition to whole slurry (WS), the
SFs and LFs had, respectively, higher and lower, concentrations of nutrients and organic
matter (OM) than the WS. The ratio of ammoniacal to total N in the LFs varied from 0.33 to
0.92 whereas the values in the SFs varied between 0.16 and 0.31. The N:P:K ratio was also
significantly influenced by the separation technique. Less than 10% of the total N applied in
the WS, SFs or LFs was found to be potentially available for plants and, in some LFs, N
immobilisation occurred after soil application. Since separation technique strongly influences
nutrient distribution between LF and SF, as well as N speciation, the choice of the
technique has to consider the final use of the resulting fractions as well as acquisition and
operating costs.
Description
Keywords
pig slurry separation techniques organic fertilizer nitrogen
Pedagogical Context
Citation
"Biosystems Engineering". ISSN 1537-5110. 113 (2012) 187-194