An approach to highly polluted wastewater management for zero liquid discharge: The case of landfill leachate

This work aims to bring the treatment of highly polluted wastewater to the concept of zero liquid discharge, using landfill leachate as a representative example. Achieving this goal involves removing pollution due to organic matter and/or heavy metals and recovering the nutrients contained in the effluent. Thus, the sequential combination of thermally activated persulfate and the Fenton reagent is proposed to eliminate the high concentration of organic matter. This avoids the need of pH adjustment to meet the Fenton process operation criteria and minimizes the amount of persulfate and, consequently, the conductivity in the treated effluent. Furthermore, this solution is particularly attractive in systems with excess energy, such as urban solid waste facilities where biogas is generated. Nutrient recovery (N in the case of landfill leachate) is carried out through precipitation in the form of struvite. Finally, if necessary, a further nanofiltration stage is proposed to minimize the conductivity of the treated effluent, making it suitable for on-site use. Under the optimized operating conditions (Flow rate: 0.5 L h(-1), residence time 60 minutes, 0.3 and 0.7 times the stoichiometric amount of persulfate (12 g/g COD0) and H2O2 (2.12/g COD0), respectively, a H2O2/Fe2+ ratio of 50/1 and 85 degrees C), a 90% removal of COD is achieved, along with 99% and 95% recovery of the nitrogen content in the effluent and reclaimed water, respectively, confirming the feasibility of this solution as an approach to a more sustainable waste management.