| In this research the micro-simulation of vertical flow constructed wetland of Coix aquatic was built, with sewage (W), nutrient solution (Y), sewage and nutrient solution (Y+W) as the irrigation water and taking intermittent water way, to analaze the situstion of plant growth parameters, change of chromium content and chemical form in matrix, chromium absorption by plants, the variation of microbial bacteria under the stress of chromium and so on, so as to deeply understanding the chromium mechanism of constructed wetland efficient removal of heavy metals in sewage, in addition the water was added in different concentration of 0,10,30 mg L-1 Cr6+ every time. The results was as follows:1. With the treatment time extension, plant height and stem diameter were both increased, while the root activity reduced; with the Cr6+ concentration increased, plant height, stem diameter, shoot dry weight, underground dry weight and root activity were decreasing, and different concentrations showed significant difference. The plant height and stem diameter in nutrient solution and sewage treatment were higher nutrient solution, sewage treatment.2. The chromium accumulation in different organs were shown:roots> leaves> stems, and roots accumulated the largest amount, different concentrations showed significant difference; with the extension of treatment time, the chromium content in roots, stems, leaves increased; with the increase of chromium addition amount, the chromium content in roots, leaves, stems showed a upward trend; thus the influence of plants in high chromium concentration treatment was more obvious.3. Compared with the pre-processing the Cr content in the matrix was increased with the extension of treatment time, along with the chromium concentration increasing the Cr content also increased. Cr content in sewage treatment was higher among three water treatment.4. Compared with the corresponding control treatment, the ex-changeable state chromium content (F1), carbonate combination state (F2), iron manganese oxides combination stage (F3), organic combination state (F4), residual state content (F5) showed a rising trend with the Cr6+ concentration increasing, different concentrations showed significant difference, and residual state content over time changes slightly, the upper matrix of various chromium state content above the middle and lower matrix.5. Upper and middle organic matter in adding chromium nutrient solution, sewage treatment increased with processing time extension and the chromium concentration increasing; sewage treatment showed a decreased trend, change trend in the lower organic matter was similar to the middle matrix. Organic matter between different concentrations showed significant difference, organic matter content in matrix different parts shown:the upper> the middle> the lower.6. Soil moisture increased with the time extension, while in nutrient solution (Y), sewage (W) treatment decreased. With the time extension and concentrations increased, effluent total chromium, hexavalent chromium content, removal rate of COD increased. Totally, hexavalent chromium content in nutrient solution (Y) was higher among three water treatment.7. With the addition of chromium, bacterial diversity decreased, but at 30 mg·L-1Cr6+ concentration, the bacterial abundance of nutrient solution, nutrient solution and sewage treatment increased. Bacterial community of samples could be devided into 37 phylums, Proteobacteria was the dominant species of soil microbial, and with the chromium concentration increased the bacterial amount of Proteobacteria decreased, while the bacterial amount of Bacteroidetes increased. In the class level Betaproteobacteria was dominant colony, with the increase of chromium concentration the bacterial amount decreased after increased first. With the chromium concentration increased, the trend of bacterial community in diffenent phylum, class level was diffenent. |
PDF Full Text Request