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Landfill leachate treatment by combination of centrifugal filter and membrane bioreactor

Proimakis Manousos

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Summary

The subject of this research is to study the treatment of landfill leachate using the combination of a Centrifugal Filter (CF) unit with a Membrane Bioreactor (MBR) unit. The leachate samples came from the landfill of Pera Galini of the municipality of Malevizi in the prefecture of Heraclion. The experiments took place in situ and the samples were later transported to the Laboratory of Design of Environmental Processes, School of Environmental Engineering, Technical University of Crete (TUC) for analysis. The samples correspond to 17 operational days from which, in the first 8 the CF processed leachates that were pretreated using coagulation-flocculation, in the next 6 the leachates were not pretreated at all and in the last 3 the leachates that were processed by the CF were pretreated by the MBR unit.Moreover in the second stage of the experiments the operating conditions of the CF had to be altered due to mechanical malfunctions. As a result the CF had its working speed reduced from the initial 12000 rpm to 3000 rpm for the last 9 days of sampling. The efficiency of the under study, landfill-leachate treatment methods was evaluated by measuring parameters such as BOD, COD, TSS, sulphates, total phosphorus, ammonium nitrogen (NH3-N), total nitrogen whereas some selected samples were tested for their concentration in chromium, zinc, iron, copper, lead and nickel.Remarkably better results arose, when the CF functioned in high speed, concerning the reduction of BOD, COD, ammonium nitrogen and total phosphorus and also the pretreatment using coagulation-flocculation resulted in even greater reductions in most of the leachate’s measured parameters. Indicative are the reduction percentages of BOD (88%), COD (86%), ammonium nitrogen (75%), total nitrogen (81%), total phosphorus ((95%) and of sulphates (91%). The examination of selected samples, corresponding to the various functioning conditions, on the reduction of the concentration of heavy metals showed that the greater decrease percentages were found for the values of nickel (94%), iron (83%), copper (61%), lead (42%), whereas the removal of zinc and chromium was less efficient.Finally the results were not what was expected from the combination of MBR-CF, concerning both the reduction of the polluting parameters and also the quality of the effluents, which did not meet the criteria in order to be discharged in the aquifer. However there is great potential and by correcting specific factors that affect negatively the treatment efficiency, this method could be used effectively as a pretreatment step in purifying landfill leachate.

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