Treatment of municipal landfill leachate by using different sorbent materials

Landfill leachate is a type of wastewater generated in a landfill and may lead to serious environmental pollution due to its complex composition. The main aim of the present research is to investigate the interaction of sanitary landfill leachate with sorbent materials, and the comparison among leachates of different origin. A better understanding of the process can lead to a cost-effective choice with the appropriate combination of the adsorption stage with other treatments. Various sorbent materials such as a commercial activated carbon (granular and powder), and two agro-industrial by-product biomaterials; grape seeds and rice husks (granular) were used. Two different samples of landfill leachates were examined. Initial samples were characterized by high COD (22 and 29 g/L), and high concentrations of nitrogen, in the form of NH₄⁺-N (2,500 and 1,100 mg/L). Since raw leachates used were characterized by high organic COD load, a dilution (1:5) of all samples was necessary. Duplicates of each sorbent (3 g) were mixed with duplicates of each leachate sample (30 mL). Experiments were carried out in glass vials sealed with Teflon caps. The kinetics of the leachates sorption on sorbent materials was investigated over a time of two months. Chemical Oxygen Demand (COD) was determined with the Standard Dichromate Reflux Method, while ammonium nitrogen determination was based on the colorimetric Koroleff method. COD reduction was more significant for the sample with the lowest initial COD value, for each sorbent material used. At the beginning (3 days) of the experiment, for the samples with the lowest initial COD value, a significant reduction of COD (~45%) by activated carbon (powder and granular) sorption was observed, while for the same sorbents but samples with the highest initial COD value, the reduction of COD reached up to ~15% and up to ~93% after 120 days. Grape seeds and rice husks showed a lower reduction of COD for both samples. COD reduction increased over time with different rates for various samples.  In addition to the reduction of the organic load, nitrogen, in the form of NH₄⁺-N, and color removal was also observed for all leachate samples. The different kinetic behavior for the two leachate samples suggests that the organic molecules present in each leachate demonstrate various sorptive behaviors with different affinity for each sorbent.

 

Acknowledgment

We acknowledge support of this work by the project “Research Infrastructure on Food Bioprocessing Development and Innovation Exploitation – Food Innovation RI” (MIS 5027222), which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).