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Article

Treatment of a Mature Landfill Leachate: Comparison between Homogeneous and Heterogeneous Photo-Fenton with Different Pretreatments

1
Department of Chemical Engineering and Materials, Facultad de Ciencias Químicas, Ciudad Universitaria s/n, Complutense University of Madrid, 28040 Madrid, Spain
2
School of Bioenergy, Agronomic, and Forestry Industry Engineering, Campus Duques de Soria, University of Valladolid, 42005 Soria, Spain
*
Author to whom correspondence should be addressed.
Water 2019, 11(9), 1849; https://doi.org/10.3390/w11091849
Received: 15 July 2019 / Revised: 23 August 2019 / Accepted: 2 September 2019 / Published: 5 September 2019
(This article belongs to the Special Issue Advances in Water and Wastewater Monitoring and Treatment Technology)
This study focuses on the treatment of a mature landfill leachate by coagulation and photo-Fenton at different conditions. Optimal coagulation is carried out with ferric chloride in acid conditions; and with alum in near-neutral conditions, to minimize the use of sulphuric acid for pH adjustment (1 g/L vs. 7.2 g/L), the generation of sludge and the increase of conductivity in the final effluent. In both cases, a similar chemical oxygen demand (COD) removal is obtained, higher than 65%, which is high enough for a subsequent photo-Fenton treatment. However, the removal of absorbance at 254 nm (UV-254) was significantly higher with ferric chloride (83% vs. 55%), due to the important removal of humic acids at acid pH. The best results for coagulation are 2 g/L ferric chloride at initial pH = 5 and 5 g/L alum at initial pH = 7. After coagulation with ferric chloride, the final pH (2.8) is adequate for a homogeneous photo-Fenton using the remaining dissolved iron (250 mg/L). At these conditions, using a ratio H2O2/COD = 2.125 and 30 min contact time, the biodegradability increased from 0.03 to 0.51. On the other hand, the neutral pH after alum coagulation (6.7) allows the use of zero valent iron (ZVI) heterogeneous photo-Fenton. In this case, a final biodegradability of 0.32 was obtained, after 150 min, using the same H2O2/COD ratio. Both treatments achieved similar results, with a final COD, UV-254 and color removal greater than 90%. However, the economic assessment shows that the approach of ferric chloride + homogeneous photo-Fenton is much cheaper (6.4 €/m3 vs. 28.4 €/m3). Although the discharge limits are not achieved with the proposed combination of treatments, the significant increase of the pre-treated leachate biodegradability allows achieving the discharge limits after a conventional biological treatment such as sequencing batch reactor, which would slightly increase the total treatment cost. View Full-Text
Keywords: landfill leachate treatment; coagulation; photo-Fenton; ZVI; biodegradability landfill leachate treatment; coagulation; photo-Fenton; ZVI; biodegradability
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MDPI and ACS Style

Tejera, J.; Miranda, R.; Hermosilla, D.; Urra, I.; Negro, C.; Blanco, Á. Treatment of a Mature Landfill Leachate: Comparison between Homogeneous and Heterogeneous Photo-Fenton with Different Pretreatments. Water 2019, 11, 1849. https://doi.org/10.3390/w11091849

AMA Style

Tejera J, Miranda R, Hermosilla D, Urra I, Negro C, Blanco Á. Treatment of a Mature Landfill Leachate: Comparison between Homogeneous and Heterogeneous Photo-Fenton with Different Pretreatments. Water. 2019; 11(9):1849. https://doi.org/10.3390/w11091849

Chicago/Turabian Style

Tejera, Javier, Ruben Miranda, Daphne Hermosilla, Iñigo Urra, Carlos Negro, and Ángeles Blanco. 2019. "Treatment of a Mature Landfill Leachate: Comparison between Homogeneous and Heterogeneous Photo-Fenton with Different Pretreatments" Water 11, no. 9: 1849. https://doi.org/10.3390/w11091849

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