Enhanced sludge dewaterability by a novel MnFe2O4-Biochar activated peroxymonosulfate process combined with Tannic acid

The high moisture content of sludge is a key factor limiting its subsequent treatment and disposal. Herein, a novel method of MnFe2O4-biochar (MFB) activated peroxymonosulfate (PMS) combined with tannic acid (TA) was conducted to improve sludge dewatering. The effects of different concentrations of MFB, PMS, and TA on waste activated sludge (WAS) dewaterability were investigated. The water content of sludge cake dropped to 40.80% when the initial pH was 5.0, and the concentration of PMS, MFB, and TA was 0.64 mM/g DS, 100 mg/g DS, and 0.12 mM/g DS respectively, demonstrating that MFB/PMS/TA could effectively enhance sludge dewaterability. Analyzing the changing of sludge properties and characterizing MFB confirmed that the enhancement of sludge dewaterability occurred in two phases. First, TA accelerated the valence transformation of Fe and Mn to promote PMS activation, which strengthened the oxidation capacity of the system. Second, TA complexed and precipitated protein to enhance the compressibility and dewaterability of sludge. Furthermore, MFB/PMS/TA treatment could increase the calorific value of treated sludge, and after the combined treatment, the sludge biochar also had a better pore structure, indicating that the sludge after the combined treatment posed a good prospect of resource utilization. These findings provide a novel strategy for the practical application of achieving efficient sludge deep dewatering, providing a valuable reference for downstream sludge utilization.