Keywords: 
• anaerobic digestion /
• phosphrus removal /
• biological process /
• physical sedimentation /
• chemical precipitation

Abstract: Batch experiments were carried out to research the contribution of biological， physical and chemical process to phosphrus removal from piggery wastewater under anaerobic condition. The results indicated that through 6 days’ anaerobic digestion， phosphrus was hardly removed from the mixed liquor which was sterilized， and the total phosphorus removal rate of supernatant of the mixed liquor without sterilization was 57.3％. Along with the decreasing total phosphorus content in mixed liquor， phosphrus in absorption solution increased， which revealed that a part of phosphate in the wastewater was released out by changing into gaseous phosphate. While the bottles contained original wastewater were sealed anaerobically and layed up for 6 days at 4℃， the total phosphorus removal rate of supernatant of the mixed liquor was 70.7％. It indicated that phosphrus removed by physical sedimentation was obvious. Detected matrix-bound phosphine in the sludge before and after anaerobic process， it was found that the content of Ca，Mg-RP（HCl-RP）in the sludge without and with sterilization increased by 93.4％ and 50.5％ respectively. The pH value of mixed liquor without sterilization increased， and of mixed liquor with sterilization decreased. It showed that the environment change (pH value increase) resulted from the metabolization of microbe facilitated chemical precipitation of phosphorus compound. Which means that biology has the accessorial function of inducing chemic depositing. The experiments indicated that phosphrus removal from piggery wastewater during anaerobic digestion was the coaction of physical， chemic and biological process.