Anaerobic Digestion of Phosphorus-Rich Sludge and Digested Sludge: Influence of Mixing Ratio and Acetic Acid

Abstract

Phosphorus is a critical influencial factor in the anaerobic digestion of phosphorus-rich sludge (PRS). The anaerobic digestion of PRS and digested sludge (DS) mixed according to different proportions was studied. The result showed that the phosphorus release rate of the mixed sludge increased with the increase in DS proportion until the DS proportion was over 50%. When the mixing ratio of PRS to DS was 3:1, the specific phosphorus release rate (SPRR) was increased by 20% and the methane production was raised to 7.39 mL/g VSS. A further experiment on the concentration of the added acetic acid indicated that the phosphorus release rate also tended to rise with the increase in acetic acid until the concentration was over 500 mg COD/L. Finally, the results of the anaerobic digestion of DS and waste activated sludge (WAS) showed that there was no typical phosphorus release in the initial stage of anaerobic digestion in WAS.