Efficiency assessment of municipal landfill leachate treatment during advanced oxidation process (AOP) with biochar adsorption (BC)

Abstract

Leachate generated in landfills are characterized by high toxicity related to, high concentrations of organic and non-organic pollutants, therefore, it is advisable to use highly effective methods of their purification to prevent environmental contamination. The aim of this study was to determine the treatment efficiency of landfill leachate during the application of integrated processes: advanced oxidation (AOP) and biochar adsorption (BC). In the case of the AOP, the chemical process was the Fenton reaction in which the source of hydroxyl radicals was H₂O₂ (system I) and SPC - sodium percarbonate (system II). Leachate was derived from the regional municipal waste landfill in Silesian Province (Poland) which was characterized by the pH of 8.40, COD value was 3155 mg L^-1 and BOD was under 165 mg L^-1. The BOD/COD ratio was at a low level (0.053) that indicated low biodegradability. The applied systems allowed of the COD reduction index to the level of 549 mg L^-1 (H₂O₂+BC) and 944 mg L^-1 (SPC+BC) where the limit threshold is 125 mg L^-1. In the same case of the TOC index, these values were respectively 119 and 186 mg L^-1, where the limit value is 30 mg L^-1.This study has been aimed to estimate the toxicity of leachate treatment in integrated systems: AOP processes + biochar adsorption. Toxicity of treated and untreated leachate has been analysed by Sinapis alba and Lepidium sativum plants-based tests. It was found that while conducting the Fenton process as system I (H₂O₂) at all reagent doses, the removal efficiency of COD and TOC was 17% and 12% higher, respectively, compared to system II. The most advantageous dose of regents was 2.5:1 and biochar - 2 g L^-1. It was observed that in the SPC+BC system the roots of L. sativum and S. alba were on average 34% and 28% longer compared to the H₂O₂+BC system. Higher germination index (GI) of both tested plants, indicating lower wastewater toxicity, was recorded for the SPC+BC system.

Keywords: Biochar; Fenton process; Landfill leachate; Phytotoxicity; Sodium percarbonate.