Dewatering of sewage sludge via thermal hydrolysis with ammonia-treated Fenton iron sludge as skeleton material

[Display omitted] •The method for thermal hydrolysis coupled with skeleton material (AHFC) was developed for dewatering of sewage sludge.•AHFC can be used as a skeleton material to promote dewatering of sewage sludge.•AHFC promoted decomposition of heterocycle compounds in cake and promoted combustion of cake for nano γ-Fe2O3 in AHFC.•Fenton iron sludge can be reused to catalyze the dewatering of SS and to recover its residual energy as a solid fuel. In this study, the alkaline hydrothermal ferric carbon (AHFC), which was prepared by hydrothermal liquefaction method using Fenton iron sludge with NH3·H2O, was used as a skeleton materials for the dewatering of sewage sludge (SS) via thermal hydrolysis. NH2 functional group presented in the AHFC and nano-sized γ-Fe2O3 was anchored on the surface of AHFC. The NH2 functional group notably promoted thermal hydrolysis of SS from the increasing of TOC and TN value. γ-Fe2O3 showed adsorption effect to the water, resulting in decline of the dewatering rate of SS in present condition. When 100% of AHFC was added, dewatering rate of SS was decreased by 19.93% (at 160 °C), 4.50% (at 180 °C) and 8.34% (at 200 °C) respectively. 3D-EEM results showed that the degree of hydrolysis was deepened when AHFC was added for the intensity of soluble microbial products decline. AHFC promoted the decomposition of protein to form heterocycle compounds in the resulting cake according to in situ FTIR results. The nano γ-Fe2O3 catalysis to cake also can be observed for the activation energy was lower than blank in the range of 40˜60%. The study demonstrated concept and the effectiveness the reuse/recycle of the Fenton iron sludge for dewatering of SS.