Post treatment of composting leachate using ZnO nanoparticles immobilized on moving media

- ZnO nanoparticles immobilized on moving media were used in composting leachate post treatment.
- The main intermediate products were determined by SPE-GC-MS technique.
- Immobilized ZnO photocatalytic process effectively reduced toxicity of the leachate.
- ZnO photocatalytic process polished biologically treated composting leachates.

The capability of UV-ZnO photocatalytic process as a post treatment method for composting leachate was examined. ZnO nanoparticles immobilized on moving media were used for the first time in order to overcome the defects of photocatalytic processes such as the separation of nanoparticles in slurry systems as well as the need for more retention time in the conventional immobilized systems. The effect of factors such as pH, UVC light intensity, concentration of immobilized nanoparticles, coated area and retention time was investigated. Based on the results of experiments, the maximum simultaneous COD and color removal of 61% and 71% were achieved respectively after 240 min of radiation with 32 W UVC lamps in pH 11, in presence of 60 gr/m2 immobilized ZnO and 400 cm2 coated area. These values indicate 20% and 23% increase in COD and color removal compared with the maximum coatable surface on the reactor respectively. SPE-GC-MS analysis also revealed that the composting leachate contained various groups of organic compounds; most of which could be degraded into lower molecular weights, using photocatalytic process. In this research, the biodegradability of the leachate was also improved from 0.15 to 0.55 and the toxicity reduced by more than 79%.

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