Combination of coagulation, Fe<sup>0</sup>/H<sub>2</sub>O<sub>2</sub> and ultra-high lime aluminium processes for the treatment of residual pollutants in biologically-treated landfill leachate
Creators: name: Bai, Xue
name: Mu, Shiqi
name: Song, Bowen
name: Xie, Mingde
Publisher: name: Taylor & Francis
Year: 2022
Subjects: subject: Physical Sciences not elsewhere classified
subject: Microbiology
subject: FOS: Biological sciences
subject: Physiology
subject: Biotechnology
subject: Environmental Sciences not elsewhere classified
subject: Chemical Sciences not elsewhere classified
subject: Immunology
subject: FOS: Clinical medicine
subject: Biological Sciences not elsewhere classified
subject: Marine Biology
subject: Inorganic Chemistry
subject: FOS: Chemical sciences
subject: Infectious Diseases
subject: FOS: Health sciences

description: Refractory substances (humus) and salts (chloride (Cl<sup>−</sup>) and sulphate (SO<sub>4</sub><sup>2−</sup>) ions) remain in the biotreated landfill leachate treatment, and it is necessary to carry out further treatments by a suitable method before discharge. In this study, the effect and operational mechanism of a combination of the coagulation Fe<sup>0</sup>/H<sub>2</sub>O<sub>2</sub> and ultra-high lime aluminium (UHLA) processes for the treatment of refractory organic substances and salts in the leachate effluent of a semi-aerobic aged refuse biofilter (SAARB) were investigated. The results showed that polyferric sulphate is a relatively efficient coagulant comparing to FeCl<sub>3</sub>, Al<sub>2</sub>(SO)<sub>4</sub>, and polyaluminium chloride. The Fe<sup>0</sup>/H<sub>2</sub>O<sub>2</sub> process further removed refractory organics from wastewater, achieving 49.8% of total organic carbon removed. Further treatment by the UHLA process was carried. The results demonstrated that the amount of precipitant, reaction duration, and temperature had a significant impact on the Cl<sup>−</sup> and SO<sub>4</sub><sup>2−</sup> removals. After three treatments, the cumulative SO<sub>4</sub><sup>2−</sup> and Cl<sup>−</sup> removal efficiencies were 98% and 80%, respectively. The SO<sub>4</sub><sup>2−</sup> and Cl<sup>−</sup> were removed in the form of precipitates such as UHLA, specific components of which included calcium alumina, Fremy's salt of calcium, aluminium chloride, and calcium hydroxide. Overall, the UV<sub>254</sub>, CN, Cl<sup>−</sup>, and SO<sub>4</sub><sup>2−</sup> removal efficiencies from the SAARB effluent were 94.08%, 98.73%, 79.96%, and 98.44%, respectively, for the combined coagulation Fe<sup>0</sup>/H<sub>2</sub>O<sub>2</sub> and UHLA processes. Therefore, the combined processes could effectively remove residual pollutants in the biologically-treated landfill leachate, and the study provides a useful reference for the removal of refractory organic matter and salts in landfill leachate. <b>Highlights</b>Coagulation-Fe<sup>0</sup>/H<sub>2</sub>O<sub>2</sub>-UHLA process is effective to SAARB effluent treatment.Refractory organics are substantially degraded by the coagulation-Fenton-like stage.Both Cl<sup>−</sup> and SO<sub>4</sub><sup>2−</sup> in SAARB effluent are greatly removed by UHLA process. Coagulation-Fe<sup>0</sup>/H<sub>2</sub>O<sub>2</sub>-UHLA process is effective to SAARB effluent treatment. Refractory organics are substantially degraded by the coagulation-Fenton-like stage. Both Cl<sup>−</sup> and SO<sub>4</sub><sup>2−</sup> in SAARB effluent are greatly removed by UHLA process.