Supercritical water oxidation treatment of humic acid as a model organic compound of landfill leachate

Abstract

Landfill leachate is a complex and variable effluent, rich in organic and inorganic matters resistant to decomposition, and is an extreme pollutant. Humic acids (HA) are some of the most refractive substances in the leachates, which is the reason why they have been used as an organic model. The degradation of an HA solution through supercritical water oxidation (ScWO) was evaluated under a constant pressure of 22.5 MPa, temperatures from 400°C to 600°C, and reaction times from 15 to 60 seconds. The results showed that the most influential factor was temperature and it guided the operational conditions of the ScWO for the landfill leachate (22.5 MPa, 600°C, and 60 seconds). The landfill leachate treatment promoted high removal rates of true colour (87%), total dissolved solids (94%), nitrate (70%), and total phosphorus (96%). In addition, it removed 57% of the COD, which was similar to the HA removal rate (61%) under the same operational conditions. This indicates that HA are an adequate organic model for landfill leachates. The results suggest that ScWO is a clean and promising treatment technology that can be applied to landfills and can have even better results if used in combination with oxidizers and catalysts, or with the use of higher temperatures.

Estimation of Leachate Volume and Treatment Cost Avoidance Through Waste Segregation Programme in Malaysia

“…Previous studies have shown that photocatalysis can remove 61% to 85% of COD and 52% of phthalates in leachate (Azadi et al, 2021;Eslami et al, 2021). AOPs, specifically using supercritical water oxidation (ScWO) as a reagent, can remove 96% of phosphorus, 70% of nitrate, 94% of total dissolved solids, and 87% of true colour (Martins et al, 2020). EO can effectively remove 68% of COD and 40% of total organic carbon (Yan et al, 2021).…”

An Overview of Treatments for Ultraviolet Quenching Substances (UVQS) and Per- and Polyfluoroalkyl Substances (PFAS) Removal from Landfill Leachate

“…Subcritical water catalytic oxidation [74], supercritical water oxidation [75], and catalyzed wet oxidation [76] also demonstrated efficiency in the treatment of leachate UVQS, showing 66, 61, and 93% of HA removal, respectively. The elevated chemical cost generally restricts the possible use of these treatments [19].…”