Study on treating old landfill leachate by Ultrasound–Fenton oxidation combined with MAP chemical precipitation

Abstract

In this study, the “Ultrasound/Fenton oxidation – MAP chemical precipitation” method was used to remove chemical oxygen demand (COD) and ammonia nitrogen from the old landfill leachate which was collected from one sanitary landfill in Wuhan. Firstly, Ultrasound treatment and Fenton oxidation treatment were separately used to treat the old landfill leachate, and under their optimum reaction conditions, the COD concentration was degraded from 842 to 697 mg L−1 and from 842 to 133 mg L−1, respectively. Then, Ultrasound/Fenton oxidation treatment was used to treat the same old landfill leachate. Compared with the single Fenton treatment, Ultrasound/Fenton oxidation treatment could raise the COD removal efficiency from 84.05 to 90.88% with the same H2O2 consumption. After the Ultrasound/Fenton oxidation treatment, Na2HPO4·12H2O and MgSO4·7H2O were used as precipitation reagents to remove ammonia nitrogen from the old landfill leachate, and the ammonia nitrogen concentration degraded from 910 to 11 mg L−1. The experiment results indicated that “Ultrasound/Fenton oxidation – MAP chemical precipitation” method was an effective and economic method to treat old landfill leachate.