Ammonia recovery from landfill leachate using gas-permeable membranes: Comparison of membrane fibers and expanded membrane tubes in both in-situ and shell-tube configurations

Abstract

This study rigorously assessed the efficacy of gas-permeable membrane (GPM) technologies in recovering ammonia from landfill leachate, focusing on polypropylene (PP) and expanded polytetrafluoroethylene (ePTFE) membranes within in-situ (INS) and shell-tube (ST) configurations. The research spanned an array of determinants, including influencing factors, sustained operational efficiency, fouling dynamics, and recovery product purity. It was established that the INS-ePTFE configuration demonstrated formidable recovery capabilities and durable performance after fouling cleaning, with ammonia removal efficiency resurging to its initial state and stabilizing at 93 % post-maintenance. In contrast, the ST-PP configuration experienced an unrecoverable drop in removal efficiency to 83 %. Fouling analysis indicated that ePTFE membranes retained structural stability against organic and inorganic deposition, with humic substances and metal carbonates as predominant constituents. Conversely, PP membranes exhibited a decline in hydrophobic properties and structural integrity upon contamination. Furthermore, pH elevation significantly enhanced ammonia nitrogen mass transfer coefficients without increasing osmotic water transfer in INS systems. The INS system also showed promise for synergistic phosphorus recovery within the pH of 9 to 10. Then, NO3–, SO42- and humic acid did not impede ammonia translocation, whereas a 1.5 % mass fraction of Ca2+ incurred a roughly 30 % reduction in ammonia mass transfer coefficients across each system. The recovery of high purity (NH4)2SO4 attested to the exceptional retention capabilities of GPMs for organics and ions, with rejection rates surpassing 99.6 %. The comprehensive analysis underscored the operational superiority of the INS-ePTFE configuration in ammonia recovery.