Multi-grade biological tank+MBR (Membrane Bioreactor) treatment system for strengthened denitrification of landfill leachate

The invention provides a multi-grade biological tank+MBR (Membrane Bioreactor) treatment system for strengthened denitrification of landfill leachate. The multi-grade biological tank+MBR treatment system comprises a multi-grade biological tank and an external type ultra-filtration membrane assembly, wherein the multi-grade biological tank is formed by connecting multi-grade denitrification-nitrification tanks in sequence; a final output of the multi-grade biological tank is connected with the external type ultra-filtration membrane assembly through a centrifugal pump and a pipeline; the landfill leachate is conveyed into each grade of a denitrification tank through a pipeline; and an outlet of the external type ultra-filtration membrane assembly is communicated with a primary-grade denitrification tank and the next working section respectively. Compared with a traditional two-grade A/O+MBR biological treatment system, the treatment system has the advantages of no reflowing of a mixed solution and reduction of