Recent progress in persulfate to improve waste activated sludge treatment: Principles, challenges and perspectives

Persulfate is considered as a promising oxidant, thus the improvement of waste activated sludge (WAS) treatment with persulfate was widely regarded as a promising technology and had been intensively investigated in recent years. However, doubts and debates about its technical and economic viability in full-scale scenarios have been raised. Interestingly, so far, no efforts have been made on either systematic summarization or critical thinking of the application of persulfate to improve WAS treatment. Therefore, it is time to assess whether and how to utilize persulfate in future WAS treatment. The present paper provided an extensive review of the mechanisms, potentials and application of persulfate in WAS treatment. The current understanding of the activation modes and mechanisms of persulfate in sludge treatment were described. Besides, the performance, mechanism and disadvantages of persulfate-based pretreatment in fermentation, digestion and dewatering process were discussed, and the role of persulfate on the removal and control of the toxicity in sludge was paid special attention. The results showed that the oxidant and interaction with microorganisms of persulfate played an important role in improving sludge treatment. Knowledge gaps and current limitations of the persulfate-based applications were identified, and perspectives on the development of persulfate-based applications were discussed. Persulfate-based technology has a great potential in improving WAS treatment, but the practical application of this technology still needs further development and larger scale demonstration. Overall, this review provided a comprehensive current understanding, future directions, and insights into issues related to the application of persulfate to improve WAS.