Journal
CLEAN TECHNOLOGIES AND ENVIRONMENTAL POLICY
Volume 19, Issue 2, Pages 541-551Publisher
SPRINGER
DOI: 10.1007/s10098-016-1245-5
Keywords
Combined treatment; Landfill leachate; Fenton-like process; Biological treatment; Ferric sludge reuse; Water exchange ratio
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Funding
- European Union through the European Regional Development Fund Project CHEMBIO [3.2.0802.11-0043]
- Estonian Ministry of Education and Research [IUT20-16]
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This pilot study describes a three-stage continuous process for treating landfill leachate containing significant concentrations of recalcitrant organic substances. The proposed technological scheme consisted of an activated sludge pre-treatment combined with a Fenton-like process enhanced by continuous sludge reuse and followed by an activated sludge post-oxidation. Biological pre-treatment removed > 99, 86, > 99, 83 and 86 % of BOD7, COD, NH4 (+)-N, phenols and the sum of lignin and tannins, respectively. Operational conditions in the ferric sludge-catalysed Fenton-like process stage were carefully adjusted in order to maintain the efficacy and practicability of combined treatment scheme. Although the application of ferric sludge as a catalyst in the Fenton-like oxidation reduced COD removal efficiency by 32 % as compared to the conventional Fenton process, lower process efficiency was compensated by reducing the water exchange ratio to 50 % without increasing the consumption of reagents. Moreover, an intermittent addition (added to every second treatment cycle) of fresh ferrous iron catalyst at a H2O2/Fe2+ w/w ratio of 20/1 increased the BOD7/COD ratio from 0.04 to 0.32 and resulted in 60 % COD removal. A cyclic addition (added to every treatment cycle) of the same amount of catalyst increased the BOD7/COD ratio from 0.09 to 0.32, and a 10 % higher COD removal efficiency as compared to intermittent catalyst addition was achieved. Finally, biological post-treatment of the leachate resulted in more than 95 % removal of each measured parameter. Overall, the combined technological scheme with continuous ferric sludge reuse in the Fenton-like stage proved promising alternative for landfill leachate treatment.
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