Enhanced silicon bioavailability of biochar derived from sludge conditioned with Fenton's reagent and lime

Biological wastewater treatment generates a large quantity of sewage sludge that requires proper treatments. In this study, the biochar pyrolyzed by sludge conditioned with Fenton's reagent and lime (referred to as Fenton -lime system) was first used as an efficient silicon fertilizer for rice cultivation. When the pyrolysis temperature was 750 degrees C, the dissolved silicon and available silicon contents in biochar derived from sludge conditioned with Fenton-lime system were much higher than those in raw sludge derived biochar without conditioning (3.49 vs. 0.72, 77.25 vs. 2.33 mg/g dry solid, respectively). The enhanced available silicon content was attributed to the newly formed calcium aluminosilicate from the reactions between the added lime and silicon-rich phases in sludge. The rice cultivated with biochar derived from Fenton-lime conditioned sludge showed improved bio-mass of stem and root by 76.85% and 36.11%, respectively, compared to blank group without the addition of Si source. Heavy metals and the reactive oxygen species (ROS) accumulation in rice were not observed after a culture period of 30 days in the application of sludge-derived biochar as silicon fertilizer. This study provides a promising approach for sewage sludge recycling as an efficient silicon fertilizer in silicon-deficiency land. (c) 2021 Published by Elsevier B.V.

Automated summary

The study utilized biochar pyrolyzed by sludge conditioned with Fenton's reagent and lime as an efficient silicon fertilizer for rice cultivation, resulting in improved growth performance of rice plants and reduced accumulation of heavy metals and ROS. This approach presents a promising method for recycling sewage sludge as a silicon fertilizer in silicon-deficiency land.