Proteins in hydrothermal carbonization liquor of sewage sludge interfere with vivianite crystallization for phosphorus recovery
Yue Zhang (Beijing Forestry University)
Xiaofan Yang (Beijing Forestry University)
Xinran Zhang (Beijing Forestry University)
Dezhi Sun (Beijing Forestry University)
Xinyi Liu (Beijing Forestry University)
Rui Lan (Beijing Forestry University)
Min Zheng (University of New South Wales)
Mark C.M. van Loosdrecht (TU Delft - BT/Environmental Biotechnology)
Xiang Cheng (Beijing Forestry University)
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Abstract
Hydrothermal carbonization (HTC) liquor of waste activated sludge generated during urban sewage biotreatment contains high concentrations of phosphate and thus is an appropriate resource for phosphorus recovery. The influence of proteins in the HTC liquor on vivianite crystallization, as a promising phosphorus recovery method, was investigated in this study from the perspectives of removal efficiencies and product properties. The proteins in the HTC liquor were observed to remain in unhydrolyzed forms with free amino acids having a negligible concentration. For vivianite crystallization in the synthetic HTC liquor with bovine serum albumin (BSA) mimicking the unhydrolyzed proteins, the efficiencies of phosphorus removal and crystallization at pH 6 decreased by 13.5 % and 18.4 %, respectively, compared with the BSA-free controls. The strong interaction between Fe and the proteins was suggested to be responsible for the reduced efficiency of vivianite formation and the variation of crystal growth mode from spirally expanding to x/z-axis extending.