The ongoing paradigm shift in sewage management from pollution control to resource recovery is an integral part of a circular economy. Efforts have traditionally concentrated on the recovery of organic carbon as bioenergy, and nitrogen and phosphorus as nutrients. In the past decade, technologies have been developed to recover high-value commodities. Simultaneously, innovative processes have been proposed to produce chemical agents that can be immediately reused in the sewage system to facilitate sewage management. This Review evaluates these latest developments and the underpinning scientific discoveries, identifies the key challenges, and outlines a roadmap towards greener and more sustainable sewage management.@en

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.

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