Method and system for treating mature landfill leachate

A method for treating a mature landfill leachate, comprising the following steps:

• subjecting the mature landfill leachate to autotrophic biological nitrogen removal to obtain a nitrogen removal solution;
• mixing the nitrogen removal solution with a coagulation adsorbent, and conducting coagulation precipitation to obtain a coagulation precipitation solid and a coagulation precipitation solution;
• subjecting the coagulation precipitation solid to humus extraction to obtain a crude humus product and a humus extraction residue;
• subjecting the crude humus product to hydrothermal reaction, and subjecting a liquid phase product obtained by the hydrothermal reaction to polymerization to obtain an aggregation medium;
• wherein the coagulation adsorbent comprises an adsorption reagent and the aggregation medium;
• subjecting the coagulation precipitation solution to electrochemical oxidation to obtain an electrochemical oxidation solution and an electrochemical oxidation residue;
• mixing the electrochemical oxidation solution with a nitrogen and phosphorus removal agent, and conducting deep nitrogen and phosphorus removal to obtain a deep nitrogen and phosphorus removal solution and a deep nitrogen and phosphorus removal residue, wherein the nitrogen and phosphorus removal agent comprises pyrite particles and/or ferrihydrite particles;
• and the deep nitrogen and phosphorus removal is sulfur autotrophic denitrification (SAD)-anaerobic ammonium oxidation (anammox) and chemical phosphorus removal;
• and
• subjecting the humus extraction residue, the electrochemical oxidation residue, and the deep nitrogen and phosphorus removal residue to phosphorus recovery to obtain a supernatant and a crude vivianite product.