Comparison of different coagulants to improve membrane distillation performance for landfill leachate concentrate treatment

Abstract

This study investigated the impacts of different coagulants on the performance of membrane distillation (MD) for landfill leachate concentrate treatment. Three common coagulants, including polyaluminum chloride (PAC), polyferric sulfate (PFS), and ferric chloride (FeCl₃), were compared at different dosages. MD performance was then evaluated regarding both contaminant retention and membrane fouling in the treatment of coagulated leachate concentrate. Results show that the three coagulants exhibited desirable performance for floc formation and thus the removal of organic matter, mainly humic substances (>80% as indicated by total organic carbon), at a dosage of 1200 mg L⁻¹. As such, coagulation enhanced the MD performance for contaminant removal and fouling mitigation with the highest increase in ammonium retention from 48.3% to 90.1%. Of the three coagulants, PFS was the most effective for improving MD capability for the retention of heavy metals and volatile organic compounds. Furthermore, PFS could synergistically remove organic and inorganic foulants (e.g. humic acid, and calcium and magnesium ions) in the coagulation of landfill leachate concentrate to alleviate membrane fouling in subsequent MD operation.