Characteristics of Phosphorus Forms in Sediments of Multilevel Digestate Stabilization Ponds in a Large-scale Swine Farm

A large-scale swine farm was selected for fixed monitoring to study the change characteristics of phosphorus forms in sediments of multilevel digestate stabilization ponds. The standards, measurement and testing (SMT) method was used to analyze the contents of total phosphorus (TP), inorganic phosphorus (IP), organic phosphorus (OP), NaOH-extracted phosphorus (NaOH-P) and HCl-extracted phosphorus (HCl-P). The results show that the contents of various forms of phosphorus in the sediment of 0-10 cm depth were higher than those in the sediment of >10-20 cm depth. In addition, their contents in the primary stabilization pond (S1) were higher than those from the secondary stabilization pond (S2). The change trend of various phosphorus in the S1 was HCl-P > NaOH-P > OP; while that in the S2 was OP > NaOH-P > HCl-P. The proportion of HCl-P, which was considered as the stable form, in the sediment of 0-10 cm was higher than that in the sediment of >10-20 cm, and higher in S1 than in S2. The results indicate that the phosphorus in the deep layer of sediment is more active than that in the superficial layer. The study will provide a reference for reasonable utilization of phosphorus of sediment of stabilization ponds in animal farms.