A techno-economical assessment of treatment by coagulation-flocculation with aluminum and iron-bases coagulants of landfill leachate membrane concentrates

Landfill leachate treatment involved with the membrane bioreactor (MBR) combined with membrane treatment via nanofiltration (NF) and/or reverse osmosis (RO) is widely used in Turkey. This treatment produces landfill leachate membrane concentrates (LLMCs) with an undesirably high concentration of contaminants. In the study, two different nanofiltration concentrates of leachate were coagulated. Coagulant dosages from 0.10 to 5.0 g of Me3+/L (Me3+: Al3+ or Fe3+), and the pH values ranged from 4.0 to 8.0 and 3.0-9.0 for Al-based and Fe-based coagulants, respectively. The most efficient pH values were 5.0 and 4.0 for Al3+ and Fe3+, respectively. These pH values are lower than those known to be effective in coagulants. The reason for this is the presence of humic substances in the wastewater. The cost of Fe2(SO4)3.xH2O was the lowest than other coagulants at the end of the cost analyses obtained from Istanbul region landfill leachate NF concentrate (NFCL-1) and Kocaeli region landfill leachate NF concentrate (NFCL-2). Under optimum conditions, the costs for NFCL-1 and NFCL-2 were calculated as 0.55 and 0.46 $/removed kg COD, respectively.

Automated summary

Landfill leachate treatment in Turkey commonly utilizes a combination of membrane bioreactor (MBR) and membrane treatment using nanofiltration (NF) and/or reverse osmosis (RO). This process yields landfill leachate membrane concentrates (LLMCs) that have high concentrations of contaminants. In this study, two different nanofiltration concentrates of leachate were subjected to coagulation. The most effective pH values for the coagulants were found to be 5.0 for Al3+ and 4.0 for Fe3+, which are lower than the typically recommended pH values due to the presence of humic substances in the wastewater. Among the coagulants analyzed, Fe2(SO4)3.xH2O had the lowest cost.