Integration of two-stage membrane distillation and fenton-based process for landfill leachate treatment: Ammonia and water recovery and advancement towards zero liquid discharge

The recovery of resources from landfill leachate (LL) represents a more sustainable approach, as it combines meeting release standards with the valorization of raw materials and contributing to the circular economy. Therefore, this study aims to evaluate the performance of a two-stage Direct Contact Membrane Distillation (2S-DCMD) for the recovery of water and ammonia from LFL integrated with the Fenton-based process for the treatment of the membrane concentrate generated in the second stage, aiming to obtain zero effluent discharge. In the first stage, the hot LFL flows through the shell side of the polypropylene hollow fiber membrane module, while the sulfuric acid solution passes through the lumen side·NH3 is recovered in the form of ammonium sulfate. In the second stage, the hot effluent from the first stage flows through the hot channel of the poly(tetrafluoroethylene) sheet membrane module, while the cooled distilled water flows through the other side in countercurrent. Despite the high efficiency of MD, disposing of the concentrate presents challenges, as pollutant concentrations can escalate by an additional 25 % to 50 % compared to the original contaminants in the raw feed. To address this issue, an advanced oxidative process of Fenton (AOP/Fenton) was optimized for treating the concentrate. In the first stage, NH3 removal reached 97.84 %, accompanied by a recovery rate of 79 %. In the second stage, a permeate with high quality was produced. Substantial removal rates were observed in this stage: colour (99.96 %), turbidity (99.89 %), COD (99.33 %), and Sulfates (90.08 %). The AOP/Fenton under optimal conditions (21.50 g/L of Fe2+ and 80 mL of H2O2) the removal of COD was 88.69 %. Thus, this route emerges as a viable alternative for landfill leachate treatment with the recovery of important resources.