Tertiary treatment of landfill leachates by adsorption.

The leachates produced at the municipal solid waste (MSW) landfill of Asturias (Spain) were submitted to a biological treatment consisting of a pressurized nitrification-denitrification process followed by ultrafiltration. The effluent from this treatment plant has a high chemical oxygen demand : biochemical oxygen demand (COD : BOD( 5)) ratio (about 25 : 1). The COD values of the effluent are above the discharge limits permitted by current legislation and therefore require a final treatment. In the present study, adsorption was investigated as a possible post-treatment. Three activated carbons (Organosorb 10, Organosorb 10MB and Filtracarb CC65/1240) were selected and equilibrium and column data were obtained. The best results were obtained with Organosorb 10MB, although adsorption capacities obtained were low and equilibrium was unfavourable. Adsorption capacities ranged between 150 and 157 mg COD g(-1) for an activated carbon dosage of 1 mg L(-1) and between 13.3 and 18.4 mg COD g(-1) for a dosage of 20 mg L(-1). As regards colour, adsorption capacities ranged between 145 and 175 UPtCo g(-1) for the lower dosage and between 16 and 29 UPtCo g(-1) for the higher dosage. Removal efficiency increased with the dosage of activated carbon employed, obtaining maximum COD and colour removals of 63 and 45%, respectively, for a dosage of 20 mg L(-1) after 5 h contact time.