Effect of Fulvic Acid in Landfill Leachate Membrane Concentrate on Evaporation Process

Abstract

Landfill leachate membrane concentrate (LLMC) poses risks to the environment and is commonly treated by evaporation. As the main component of the dissolved organic matter in LLMC, fulvic acid (FA) was selected as a representative to investigate its effect on evaporation and the removal efficiency by pretreatment in this study. According to the water quality indexes and three-dimensional fluorescence spectra of LLMC samples collected from five landfills in China, the concentration of total organic carbon in LLMC was 700‒2500 mg∙L−1, in which FA accounted for 50‒85%. The boiling point and viscosity of the configured FA-NaCl-Na2SO4 solution both increased significantly when FA was concentrated 20 times (approximately 30,000 mg∙L−1). Due to the presence of FA, the violent frothing phenomenon appeared at above 70 °C in evaporation, and the solubility of CaSO4·2H2O in FA-NaCl-Na2SO4 solution was significantly lower than that without FA. All these results indicated that the high FA concentration in LLMC could lead to decreased heat transfer coefficient and evaporation capacity during evaporation. Therefore, the softening pretreatment including the addition of Ca(OH)2, Na2CO3, and coagulants was employed to reduce the hardness and FA concentration. After the softening experiments, the removal efficiency of FA was >95% for the configured LLMC sample, while for the actual LLMC sample collected from landfills, the removal efficiency of FA and chemical oxygen demand could reach >80% and about 30%, respectively. The remaining concentration of FA in LLMC was about 200 mg·L−1, and the recovery efficiency of clean water could be 90% in the evaporation process. This research has important guiding significance for the evaporation treatment of LLMC.

Effective Membrane Distillation of Landfill Leachate Concentrate Using a Superhydrophobic SiO2/PVDF Membrane for Resource Recovery

“…The landfill leachate has been a highly polluted and complex waste stream, encompassing diverse organic pollutants (e.g., humic substances), inorganic salts (NaCl, heavy metal, and ammonia nitrogen), and xenobiotic compounds. , To address this challenge, the combination of a membrane bioreactor with a nanofiltration process has been preferentially applied to treat the landfill leachate, offering the inherent advantages of flexible operation, low energy consumption, and efficient efficacy for the removal of pollutants (e.g., highly loaded organic compounds, heavy metals, and ammonia nitrogen) for safe discharge of the waste stream. − However, a technical challenge arises with the generation of landfill leachate concentrate during the integrated membrane process, which typically accounts for 15–30% of the raw landfill leachate. − Compared to raw landfill leachate, treating landfill leachate concentrate is more challenging due to its elevated loading in refractory organic pollutants and salinity. Conventional methods, such as recirculation, evaporation, and incineration, have been explored for treating landfill leachate concentrate. − Nevertheless, these conventional methods exhibit specific drawbacks, which hinder their long-term viability. For instance, recirculation of the landfill leachate concentrate into the landfill may lead to accumulation of inorganic salts, remarkably impairing the performance of membrane technologies as the post treatment. − Evaporation and incineration with high energy consumption are deemed less sustainable .…”