A coagulation-flocculation process combined with continuous adsorption using eggshell waste materials for phenols and PAHs removal from landfill leachate

A sequential treatment consisting of coagulation/flocculation followed by transport column experiment was adopted and used in this work for the treatment of landfill leachate containing phenols and polycyclic aromatic hydrocarbons (PAHs). Coagulation experiment was performed in a standard jar test apparatus using alum as coagulant material. In column experiments, natural eggshell material was used as filter media after calcinations at 750oC either separately or combined with granular activated carbon (GAC). Alum addition at a predetermined optimum dose (3.5 g/L) caused a reduction in total suspended solids (TSS), chemical oxygen demand (COD), total phenols, and total (PAHs) by 82%, 32%, 24%, and 34% respectively. Specific PAHs analysis revealed higher binding affinity of more hydrophobic PAHs toward particles with 50% reduction than those of less hydrophobic PAHs with only 6% reduction. The results obtained from the transport column experiments indicate that calcined eggshell (ESC) particularly when applied as a mixture with GAC can be used as promising adsorbent for both phenols and PAHs. 95% of phenols and PAHs were removed during the first 1,500 pore volumes (PV) of column operation while > 80% were obtained at the end of the experiment (3,500 PV).