Organic Matter Characterization and Phytotoxic Potential Assessment of a Solid Anaerobic Digestate Following Chemical Stabilization by an Iron-Based Fenton Reaction

Abstract

Digestates, a byproduct of the anaerobic bioconversion of organic wastes for the production of biogas, are highly variable in chemical and biological properties, thus limiting their potential use in agriculture as soil amendment. Using a lab-scale glass reactor, we aimed to assess the feasibility to chemically stabilize the solid fraction of an anaerobic digestate by applying a Fenton reaction under constant pH (3.0), temperature (70 °C), reaction time (8 h), and various combinations of H 2 O 2 and Fe 2+ . In Fenton-treated samples, the phytotoxic potential (determined on a test plant), total phenols, and the bad smell odor index markedly declined, whereas total C and N remained unaltered. Thermogravimetric (TG) analysis and Fourier transform infrared (FT-IR) spectroscopy revealed contrasting changes in extracted humic and fulvic fractions being increased or depleted, respectively, in aromatic substances. Process feasibility and optimum conditions for an effective biomass stabilization were achieved with a H 2 O 2 / Fe 2+ ratio between 0.02 and 0.03.

WITHDRAWN: Response of chemical and biochemical soil properties to the spreading of biochar-based treated olive mill wastewater

“…The germination test was performed in the presence of OMW treated with biochar (BP or BC) and soil amended with treated OMW [ 19 , 46 , 47 ]. Briefly, Lepidium sativum L. seeds were placed in 10 × 90 mm Petri dishes (10 seeds per dish), equipped with 5 mL of OMW or 10 g of soil and incubated for 72 h at 25 ± 2 °C in the dark in a climatic chamber.…”

Response of chemical and biochemical soil properties to the spreading of biochar-based treated olive mill wastewater

“…The activity of the o -diphenol oxidase (DPO) was determined using a mixture of catechol and proline as the substrate [ 45 ]. The fluorescein diacetate hydrolase (FDAH) activity was assessed as described by Roccotelli et al [ 46 ]. Triplicates were analyzed for each activity assay.…”

“…The germination test was performed in the presence of OMW treated with biochar (BP or BC) after 60 days and soil amended with treated OMW [ 18 , 46 , 47 ]. Briefly, Lepidium sativum L. seeds were placed in 10 × 90 mm Petri dishes (10 seeds per dish), equipped with 5 mL of OMW or 10 g of soil and incubated for 72 h at 25 ± 2 °C in the dark in a climatic chamber.…”

Effect of Fenton pretreatment on enzymatic hydrolysis of poplar

“…The Fenton reaction involves the oxidation of Fe 2+ to Fe 3+ by H2O2, and then the reduction of Fe 3+ to Fe 2+ , resulting in the formation of H2O, O2, and two kinds of oxygen radicals, namely HO and HOO (Liu et al 2019c). The oxygen radicals initiate chain reactions for the oxidation of the lignocellulosic components and the further formation of other reactive oxygen species (Roccotelli et al 2020).…”