Effects of organic matter on crystallization of struvite in biologically treated swine wastewater.
A sustainable way to recover phosphorus (P) in swine wastewater involves a preliminary step of P dissolution followed by the separation of particulate organic matter (OM). The next two steps are firstly the precipitation of struvite crystals done by adding a crystallization reagent (magnesia) and secondly the filtration of the crystals. To develop the process successfully at an industrial scale, the control of the mechanisms of precipitation is the key point in order to obtain high value-added products, that is, big struvite crystals easy to harvest and handle. Experiments with process parameters optimized previously in a synthetic swine wastewater were performed on real swine wastewater to assess the role of the OM on struvite crystallization. After 24 h, with a pH increase to 6.8 only, 90% of the initial P was precipitated and 60% was precipitated as struvite. 80% of the solid recovered was in the fraction > 100 µm. The other forms recovered were brushite, amorphous calcium phosphate, NaCl, KCl and OM. The influence of OM on struvite precipitation in acidified swine wastewater was negative on the reaction kinetics but positive on the size of the struvite crystals. The presence of colloidal particles increased the size of the struvite crystals but slowed down the kinetics due to the viscosity induced by the repulsive force of the colloids. The maximum size of single struvite crystals (200 µm) was observed with the presence of particulate OM.
a IRSTEA/Cemagref , 17 avenue de Cucillé, CS 64427, 35044 Rennes Cedex , France.|c Université européenne de Bretagne (UEB) , 5 Boulevard Laënnec, 35000 Rennes , France.
Aurélie
A
Capdevielle
b ICT Prague , Department Technology of water , Technická 5, Prague 6 , 166 28 , Czech Republic.
Eva
E
Sýkorová
a IRSTEA/Cemagref , 17 avenue de Cucillé, CS 64427, 35044 Rennes Cedex , France.|c Université européenne de Bretagne (UEB) , 5 Boulevard Laënnec, 35000 Rennes , France.
Fabrice
F
Béline
a IRSTEA/Cemagref , 17 avenue de Cucillé, CS 64427, 35044 Rennes Cedex , France.|c Université européenne de Bretagne (UEB) , 5 Boulevard Laënnec, 35000 Rennes , France.
Marie-Line
ML
Daumer
D000818:Animals; D003102:Colloids / Q000737:chemistry; D003460:Crystallization / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D017616:Magnesium Compounds / Q000737:chemistry*; D008372:Manure; D010316:Particle Size; D010710:Phosphates / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry; D000069877:Struvite; D013552:Swine; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000737:chemistry*
D003102:Colloids; D017616:Magnesium Compounds; D008372:Manure; D010710:Phosphates; D010758:Phosphorus; D000069877:Struvite; D062065:Wastewater
Struvite; organic matter; phosphorus recovery; pig manure; swine wastewater