A comparative landfill leachate treatment performance in normal and electrodes integrated hybrid constructed wetlands under unstable pollutant loadings

This study provides a comparative pollutant removal performance assessment between organic or construction materials-based four hybrid wetland systems that received landfill leachate. The hybrid systems included vertical flow (VF) followed by horizontal flow (HF)-based unplanted and planted systems, and planted electrodes incorporated microbial fuel cell (MFC) integrated hybrid wetlands systems. All the systems were run in free-draining mode. Overall mean chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) removal percentage of the hybrid systems ranged between 81 and 99%, 82 and 96%, 74 and 99%, respectively, under unstable input pollutant loading conditions. Additionally, up to 27% organic and up to 14% nitrogen removal improvement was observed in electrodes integrated free-draining VF wetlands. Free-draining and additional oxygen availability from atmospheric diffusion, rootzone improved the removal performance of MFC-based VF wetlands. Input load increment decreased organic, nutrient removals in second stage HF units due to saturated media. The chemical composition of the employed media supported biotic, abiotic organic, nutrient removal pathways. Nutrient accumulation percentage in plants tissue was very low, i.e.,<= 3%. Bioenergy production across the MFC-based VF-HF wetlands decreased with input pollutant load increment. The single anode electrode-based VF wetland achieved maximum power density production, i.e., 294 mW/m(2).. The electrodes integrated hybrid systems achieved comparatively stable removal performance despite input pollutant/hydraulic load variation.

Automated summary

This study provides a comparative assessment of pollutant removal performance in four hybrid wetland systems, based on organic or construction materials, that received landfill leachate. The results showed that under unstable input pollutant loading conditions, the mean removal percentages of COD, TN, and TP in the hybrid systems ranged from 81% to 99%, 82% to 96%, and 74% to 99%, respectively. The integration of electrodes in free-draining VF wetlands led to improvements in organic and nitrogen removal. However, the removal efficiency of organic matter and nutrients decreased in the second stage HF units due to saturated media. The chemical composition of the employed media supported biotic and abiotic pathways for organic and nutrient removal. The accumulation of nutrients in plant tissues was very low, with a percentage of <=3%. The bioenergy production in the MFC-based VF-HF wetlands decreased with increasing input pollutant load. The VF wetland with a single anode electrode achieved the highest power density production of 294 mW/m(2). The hybrid systems with integrated electrodes demonstrated relatively stable removal performance despite variations in input pollutant load and hydraulic load.