Intensification of supercritical water oxidation (ScWO) process for landfill leachate treatment through ion exchange with zeolite. (1st January 2020)

• Record Type: Journal Article
• Authors: Scandelai, Ana Paula Jambers; Zotesso, Jaqueline Pirão; Jegatheesan, Veeriah; Cardozo-Filho, Lucio; Tavares, Célia Regina Granhen
• Is Part Of: Waste management. Volume 101(2020)
• Page Start: 259
• Page End: 267
• Publication Date: 2020-01-01
• Subjects: Adsorption -- Ammonia removal -- Clinoptilolite -- Leachate treatment -- ScWO; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2019.10.005
• Languages: English
• ISSNs: 0956-053X

Abstract

Graphical abstract: Highlights: Ion exchange was applied to ScWO as a subsequent step for ammonia removal. ScWO was operated without the addition of oxidants or supplementary substances. The effect of temperature and recycling on ScWO reactor were evaluated. ScWO/ion exchange system reduced 81% of TOC and 90% of NH3 -N. ScWO/ion exchange system removed color and turbidity effectively (98%). Abstract: Over the past few years, supercritical water oxidation (ScWO) has shown great potential for application to landfill leachate treatment, providing substantial organic matter degradation in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total organic carbon (TOC). However, the conversion of ammonia, which is present at high concentrations in leachates, is the rate-limiting step during ScWO and usually requires large amounts of oxidants, the addition of catalysts, or severe operating conditions. Aiming at proposing a treatment system that effectively removes both organic matter and ammonia from leachate, this paper evaluates the intensification of the ScWO process through ion exchange with zeolite. Thus, ScWO was operated under a pressure of 23 MPa at 600 and 700 °C, without the addition of oxidants. The zeolite (clinoptilolite) was used without any modification inside a glass column. The ScWO (600 °C)/zeolite system removed 90% ammoniacal nitrogen (NH3 -N), 100% nitrite (NO2 -N), 98% nitrate (NO3 -N), color, and turbidity, 81% TOC, and 74% COD, suggesting that this system is a promising alternative for leachate treatment. However, the final NH3 -N and COD values were slightly above the limits (20 and 200 mg L −1, respectively) stipulated by the Brazilian environmental legislation. These results suggest that further improvements are still required for the application of the intensified ScWO to be feasible. Notably, ammonium-saturated clinoptilolite is amenable for regeneration or can be applied to soil as a slow-release fertilizer.