Biochar was derived from rice straw pyrolyzed at 400°C, and biochar was added to the excess sludge at the ratio of 10% DS, 25% DS, and 50% DS as a supplementary skeleton for sludge Fenton pre-treatment. Rice husk biochar mixed with fungus residue as compost conditioner. In this study, we explored the effects of seven groups of composting materials on the composting effect and fertilizer quality under different pre-treatment methods of Fenton-pretreated sludge cake and conventional dewatered sludge cake, and different biochar additions. Specifically, we conducted a 22-day composting experiment using a composting reactor to investigate the effect of rice husk biochar combined with Fenton oxidation on the physicochemical properties of sludge composting. The results of this study showed that the FB50 group significantly increased the composting rate. Nutrient analysis showed that the FB50 group was rich in fertilizer nutrients, such as available phosphorus, and alkali-hydrolyzable nitrogen content increased. Heavy metals (Cu, Cd, Cr, Pb, Zn, Ni) met China's 'Agricultural Sludge Pollutant Control Standard' GB 4284-2018 Grade A standard, with obvious passivation and significantly reduced bioavailability. All these results suggested that biochar coupled with Fenton oxidation was more beneficial to sludge composting.
Keywords: Fenton oxidation; biochar; composting; excess sludge; heavy metals.