G.C. Sánchez

Improvement of Cr phytoremediation by Pistia stratiotes in presence of nutrients.

The effects of different concentrations of P and N, added separately or combined, on the Cr(III) accumulation capacity of P. stratiotes were studied. Plants and pond water with the addition of contaminant(s) were placed in plastic aquaria. Cr concentration was 5 mg L–1, while P and N concentrations were 5 mg L–1or 10 mg L–1. Nutrient addition significantly favoured Cr removal and enhanced Cr translocation to leaves. In Cr treatments a high detritus formation from loss of root biomass was observed probably due to its toxicity. Cr was mainly accumulated in the detrital fraction, whereas P and N were retained fundamentally in leaves. A toxic effect was observed in the Cr + P10 and Cr + N10 treatments. These results could be applied to enhance Cr removal efficiency of constructed wetlands using P. stratiotes, where nutrient enrichment could be attained by treating sewage together with the industrial effluents.

Physiological and biochemical responses of Eichhornia crassipes exposed to Cr (III).

The effect of exposure of Eichhornia crassipes to Cr (III) was assessed by measuring changes in photosynthetic pigments, malondialdehyde, superoxide dismutase, glutathione reductase, catalase, and guaiacol peroxidase activities, as well as Cr concentration in tissues. Cr concentration in roots was significantly higher than in aerial parts and increased with Cr concentration in water. Photosynthetic pigments increased significantly, whereas the activities of antioxidant enzymes varied differently in plant tissues. Low Cr concentrations induced a rapid response of E. crassipes during short-term exposure, implying that the antioxidant system conferred redox homeostasis. Results showed that Cr (III) was more toxic at the two highest concentrations and long-term exposure, while it was not harmful but beneficial at the two lowest concentrations and short-term exposure. This work concludes that E. crassipes was able to grow under Cr (III) stress by protecting itself with an increase in the activity of its antioxidant system.

Hybrid constructed wetlands for the treatment of wastewater from a fertilizer manufacturing plant: Microcosms and field scale experiments

Wastewater from a fertilizer manufacturing plant requires improvement prior to its environmental disposal. Ammonium is the critical contaminant to be removed. The aim of this study was to evaluate the feasibility of using free water surface wetlands (FWSWs), horizontal subsurface flow wetlands (HSSFWs), and their combination in hybrid wetlands (HWs) for the final treatment of wastewater with high ammonium concentration from a fertilizer manufacturing plant. Substrates and macrophytes were evaluated in microcosm experiments during three months. There were no significant differences in contaminant removal among HSSFWs with LECA or FWSWs planted with Typha domingensis or Canna indica. In a second stage, two configurations of pilot-scale HWs were constructed at the manufacturing facilities. Configuration A: HSSFW(A1)-FWSW(A2) and Configuration B: FWSW(B1)-HSSFW(B2) were evaluated during 12 months. There were no significant differences in contaminant removal (%) between the two configurations of HWs for COD (A: 74.5 ± 12.2/B: 81.5 ± 9.4), ammonium (A: 59.5 ± 17.5/B: 57.9 ± 21.4), nitrite (A: 79.8 ± 24.2/B: 80.6 ± 16.8) and dissolved inorganic nitrogen (DIN) (A: 59.4 ± 17.3/B: 50.3 ± 24.4). However, nitrate concentration (9.83 ± 3.11 mg N L-1) was significantly lower after Configuration A than after Configuration B (18.8 ± 5.2 mg N L-1). Comparing FWSWs and HSSFWs, they did not present significant differences in ammonium removal, while FWSWs presented the highest DIN removal. T. domingensis and C. indica in HSSFWs and T. domingensis in FWSWs tolerated wastewater conditions. T. domingensis presented the highest productivity. In further research, FWSWs in series planted with T. domingensis should be studied.