Bioremediation of landfill leachate by Aspergillus flavus in submerged culture: Evaluation of the process efficiency by physicochemical methods and 3D fluorescence spectroscopy

The present study investigates the ability of Aspergillus flavus (A. flavus) for organic and nitrogen matter removal from landfill leachate. Experiments were carried out with different types of leachate, (Young (YL), Intermediate (IL) and Old (OL)) used at different concentrations of the leachate up to 100%. The organic fraction of landfill leachate was measured by biological oxygen demand (BOD5) and chemical oxygen demand (COD) then it was qualitatively assessed using three dimensional excitation emission matrix (3D-EEM). The nitrogen fraction was measured by ammonium (NH4+) and nitrate (NO3-). The experiments revealed that, BOD5, COD and NH4+ removal rates after 4 weeks of treatment in flasks were within the ranges of 47.90-81.63%, 12.91-48.50% and 70.84-98.81%, respectively and that affected the reduction of the phytotoxicity in a positive way. A. flavus with 25% concentration of YL recorded the best results in reducing COD and BOD5 with maximum removal rates of around 48.50% and 81.63%, respectively. However, the highest NH4+ removal rate of 98.81% was found in 25% concentration of OL. The 3D-EEM results showed that the intensities of the fluorescent peaks for the three treated leachates have decreased sharply after treatment. This was confirmed by the increase of the organic matter complexity index for different treatments (from 0.55 to 0.87). Therefore, A. flavus may be potentially useful in the treatment of landfill leachate at a concentration of less than or equal to 50% as it was able to remove organic and nitrogen compounds, particularly in the treatment of YL leachate at a concentration of 25%.