Cr, Ni, and Zn removal from landfill leachate using vertical flow wetlands planted with Typha domingensis and Canna indica.

Chromium (Cr), Nickel (Ni), and zinc (Zn) removal from landfill leachate using mesocosm-scale vertical flow wetlands, the effect of recirculation, and the ability of macrophytes to retain metals were evaluated. Wetlands were filled with coarse sand and light expanded clay aggregates and planted with Typha domingensis or Canna indica. Wetlands were operated using intermittent loading, with and without recirculation. Raw leachate was diluted and spiked with metals to reach the following concentrations: 0.2 mg L-1 Cr , 0.2 mg L-1 Ni, and0.2 mg L-1 Zn and 1.0 mg L-1 Cr, 1.0 mg L-1 Ni, and 1.0 mg L-1 Zn. Wetlands planted with T. domingensis presented higher metal removal than those planted with C. indica. Recirculation enhanced metal removal efficiencies significantly, being for T. domingensis/C. indica: 60/54, 49/47, 61/47% for Cr, Ni, and Zn at 0.2 mg L-1, and 80/71, 76/62, 73/59% for Cr, Ni, and Zn at 1.0 mg L-1, respectively. Metals were efficiently retained by macrophytes. Plant biomass and metal concentrations in roots were significantly higher than in shoots. Scanning electron microscopy and X-ray microanalysis showed that metals were absorbed by internal root tissues. A hybrid wetland planted with T. domingensis may be implemented to improve not only metal but also chemical oxygen demand and total nitrogen removals.

Selection of macrophytes and substrates to be used in horizontal subsurface flow wetlands for the treatment of a cheese factory wastewater.

The aims of this study were to select the most suitable macrophyte species and substrate to be used in horizontal subsurface flow (HSSF) wetlands for the treatment of a local cheese factory wastewater, and to quantify the influence of plant species and substrates by applying of a simple first-order kinetic model. Microcosms-scale HSSF wetlands were planted with Canna glauca or Typha domingensis. LECA and river stones were used as substrates. Both studied macrophytes showed a high tolerance to the treated wastewater. HSSF wetlands were efficient for the treatment of diluted cheese production wastewater. COD, TP, NH4+-N and TN showed high removal efficiencies in all the HSSF wetlands. HSSF wetlands planted with C. glauca showed the best performance for removal of NH4+-N. The highest SRP removal was obtained in HSSF wetlands planted C. glauca with LECA as substrate. A simple first-order kinetics model was applied. The fitted parameters of the modified first-order model k-C* allowed to demonstrate the effect of the plants in the treatment of the effluent. HSSF wetlands planted with C. glauca using river stones were the systems that showed the fastest TIN removal. According to the obtained results, it is proposed to use C. glauca and river stones as substrate in a HSSF wetland for the treatment of this wastewater. The present study provides useful data to design a wetland at a larger scale.

Vertical flow wetlands and hybrid systems for the treatment of landfill leachate.

Landfill leachates contain a variety of toxic compounds, which makes them one of the most difficult types of wastewater to be treated. An alternative "green" technology for leachate treatment is the use of constructed wetlands (CWs). The aims of this study were to select macrophytes and substrates to be used in vertical flow wetlands (VFWs) and to evaluate the performance of hybrid systems composed by a VFW and a horizontal subsurface flow (HSSW) or a free water surface flow (FWSW) wetlands for the treatment of a high ammonium concentration landfill leachate. In microcosms scale experiments, Typha domingensis, Scirpus californicus, and Iris pseudacorus were studied to assess their tolerance to raw and diluted leachate. Substrate selection for VFWs was evaluated using different layers of light expanded clay aggregate (LECA), coarse sand, fine sand, and gravel. Contaminant removals were higher in planted than in unplanted wetlands. Plants did not tolerate the raw effluent but showed a positive effect on plant growth when exposed to the diluted leachate. T. domingensis and I. pseudacorus showed higher contaminant removal ability and tolerance to landfill leachate than S. californicus. VFW with LECA + coarse sand showed the best performance in removal efficiencies. Hybrid system composed by VFW-FWSW planted with T. domingensis presented the best performance for the treatment of landfill leachate with high concentrations of ammonium.

Effects on Eichhornia crassipes under Zn stress.

Eichhornia crassipes is a macrophyte widely used in phytoremediation, demonstrating a high ability to remove metals from water. The aim of this work was to evaluate its enzymatic detoxification strategies and metal accumulation when it is exposed to different Zn concentrations (0, 2, 4, 6, and 9 ppm) for periods of 24, 48, and 72 h. Zn concentration in roots was significantly higher than in aerial parts. Independently of the treatment, in the first 48 h, concentrations of photosynthetic pigments were not affected. However, a significant increase (between 19 and 34%) in Chl-b concentrations for all treatments was observed at 72 h. Carotenoid concentration was not affected during the first 48 h, while at 72 h, there was a significant increase regarding the control (between 11 and 24%) for all treatments. Malondialdehyde concentration in aerial parts and roots was not affected during the experiment. Nonetheless, a significant increase in the enzymatic activity of the antioxidant system was observed. Results suggest that Zn could have potential antioxidant properties, which may result in the activation of different antioxidant enzymes involved in the protection against metal stress.