Study on the waste activated sludge dewatering effect and mechanism conditioned by persulfate induced with iron-based sludge biochar

Abstract

In order to improve the dewatering performance of waste activated sludge，iron-based sludge biochar（Iron-SBC） activating persulfate（PDS） was used to treat sludge. The effects of PDS dosage，Iron-SBC dosage，reaction time，reaction temperature and initial pH on waste activated sludge dewatering efficiency were studied，and the mechanism was also analyzed. The results showed that when the temperature was 65 ℃，the dosage of PDS per unit TSS was 150 mg/g，the dosage of Iron-SBC per unit TSS was 350 mg/g，the initial pH was 6.68，after being conditioned by Iron-SBC/PDS for 20 minutes，the sludge capillary water absorption time，sludge specific resistance and sludge cake moisture content decreased to 8.4 s，5.4×1012 m/kg and 73.5%，respectively. The mechanism analysis indicated that oxidation reaction occurred during the process. The originally tight and flat sludge flocs and extracellular polymers were cracked and the bound water was released. The highly hydrophilic tightly bound extracellular polymeric substances（TB-EPS） in sludge were transformed into loosely bound extracellular polymeric substances（LB-EPS） and soluble extracellular polymeric substances（S-EPS），and the proteins which were unfavorable to sludge dewatering were oxidized and degraded. The decrease of TB-EPS and neutralization of positive iron ions increased the Zeta potential value. Iron-SBC with rigid structure reduced the compressibility coefficient of sludge cake. At the same time，under the flocculation of Fe3+，the fractal dimension of sludge became larger. Under the coupling action of “oxidation-skeleton construction”，the waste activated sludge deep dewatering was realized.

Keywords

• iron-based sludge biochar
• persulfate
• sludge dewatering
• skeleton construction
• extracellular polymer