Use of zeolite and bauxite as filter media treating the effluent of Vertical Flow Constructed Wetlands

Various gravity filters containing zeolite, bauxite and carbonate material were constructed and operated for 3 years, to provide further treatment of the effluent of a pilot-scale Vertical Flow Constructed Wetland (VFCW). Results showed a significant improvement of the VFCW effluent quality at a residence time of 1 day. Zeolite was more effective in nitrogen and organic matter removal, while bauxite in phosphorus retention. The carbonate material had the lowest efficiency among all filter materials used. The filter containing a 50–50% mixture of zeolite and bauxite showed the highest efficiency in pollutant removals. The increase of the residence time from 1 to 2 days did not show a respective statistically significant increase in removal rates. Temperature did not significantly affect the performance of the filters, with the exception of phosphorus removal.

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► Experiments in one pilot-scale Vertical Flow Constructed Wetland.
► Wetland effluent polishing in zeolite and bauxite filters.
► Quantification of organic matter, nitrogen and phosphorus removals.
► Effects of filter material, temperature, residence time, and other parameters.
► Prediction of filter lifetime and optimization of filter design.