Multipurpose treatment of landfill leachate using natural coagulants - Pretreatment for nutrient recovery and removal of heavy metals and micropollutants

Landfill leachate is considered to be a potential source for nutrient recovery due to high ammonia concentration. However, it contains concerning pollutants such as metals and micropollutants in high levels. The coagulation-flocculation process is commonly used as a pretreatment technique to remove such pollutants. Plant-based materials have recently been explored as an alternative for conventional coagulants as the latter leave residuals that require further treatment. The use of natural coagulants for nutrient recovery purposes has not been investigated previously. This study evaluated the effectiveness of tannin-based product named HTH to improve landfill leachate quality to suite the requirements for nitrogen recovery using membrane contactor technology. The optimal combination of dosage and pH was determined using Response Surface Methodology (RSM). The parameters selected to evaluate the treatment were total nitrogen, total phosphorus, total organic carbon, and ammonia. The obtained optimized combination of dosage and pH were 11.1 mL/L and 7.3, respectively. This combination resulted in respective removal of TP, TOC and TN of 47%, 15%, and 4%, while NH3-N increased by 20%. The potency of the treatment for removing micropollutants and metals was evaluated. Highest metals removal was attained for Fe, Ti, Cr, Al, Ba and V, while other metals were removed in smaller percentages. Decent removal of cationic surfactants, phenols and pharmaceuticals such as 5-methylbenzotriazole, ibuprofen, carbamazepine, and metoprolol was also achieved with the treatment. The results of this study suggest that tannin-based materials are effective coagulants for treating landfill leachate with the goal of preparing it for nitrogen recovery.