Fenton oxidation as pretreatment for biomass gasification condensate: cost and biomass inhibition evaluation

Abstract

Gasification transforming organic compounds into energy-rich pyrolytic gas, is a climate-friendly treatment option for biological solid wastes. The condensates arising from the pyrolytic gas valorization is owing to high concentrations of small molecular phenols, cyanides, nitrogen-heterocyclics, aromatics and ammonium, posing an environmental and health hazard. In this paper, the watery phase of the biomass gasification condensate from spent mushroom compost (SMC), with a chemical oxygen demand (COD) of 16.4 g/L and total nitrogen of 2.3 g/L, was pretreated by Fenton oxidation. The experiments were conducted at room temperature with an initial pH value of 3, 5 and 8.9, hydrogen peroxide (H2O2) dosages between 15 and 100% of the normalized stoichiometric ratio (NSR), and Fe2+ dosages corresponding to molar ratio of H2O2:Fe2+ between 10 and 30. Through respiration inhibition assays, the best operational condition for detoxification was determined at an initial pH 5 with 30% NSR H2O2 dosage and molar ratio of H2O2:Fe2+ at 15:1. The specific operational cost of the Fenton oxidation was calculated at 2.17 €/kg CODelimination. In respiration inhibition assay, the oxygen consumption of wastewater after Fenton oxidation was increased by 316% in 3 days. In a 20 days’ biogas production test, the biogas production was increased by 81%. HIGHLIGHTS Detoxification of biomass gasification condensate via Fenton oxidation.; Modification of respiration inhibition assays with utilization of WTW OxiTop®-C.; Toxicity evaluation of treated wastewater by respiration inhibition assays.; Operational parameter optimization based on detoxification capabilities and cost-efficiency.; Toxicity increased by UV-mediated Fenton oxidation.;

Keywords

• cost evaluation
• detoxification
• gasification condensate
• pretreatment by fenton oxidation
• respiration inhibition assay