Enhanced performance of a direct contact membrane distillation system via in-situ thermally activated H₂O₂ oxidation for the treatment of landfill leachate

In this study, an integrated system of self-enhanced membrane distillation (MD) with H₂O₂ oxidation was explored for the efficient treatment of landfill leachate, in which the heat energy required for MD operation was harvested for H₂O₂ activation. Organic composition of the leachate was explored during the filtration processes via fluorescence excitation emission matrix combined with parallel factor analysis, which identified three different organic fractions (i.e., tryptophan-like C1, fulvic-like C2, and humic-like C3) in the extracted membrane foulants as well as in the membrane concentrate. C1 was the main organic fraction in the foulant, while C3 was dominant in the leachate concentrate. Moreover, H₂O₂ was successfully activated by the in situ thermal energy (i.e., temperature difference) and pristine Fe ions in the leachate, resulting in significant (48%) oxidation of bulk organic matter. Preferential removal of the main fouling fraction (i.e., C1) from the bulk landfill leachate occurred under the optimal H₂O₂ dose of 1.5 g/L. With respect to the H₂O₂ dose on the feed side of the assisted MD setup, there was a considerable increase in the membrane flux, a 24% higher membrane flux recovery, and 1.5 times more filtered volume, as compared to the reference run without oxidation. The addition of H₂O₂ to the conventional MD also led to a significant (93%) removal of the bio-refractory humic-like C3 fraction from the membrane concentrate. The results of this study demonstrated the successful operation of assisted MD based on the in-situ energy utilization for H₂O₂ activation, which led to a drastic improvement in the performance of the system and the production of low-strength, reclaimable leachate concentrate.