| Nowadays, eutrophication has been a serious problem for waterenvironmental, which was caused by discharging the domestic sewage intorivers and lakes in a large amount without treatment. There are variestechnical methods for domestic sewage treatment, and the constructed wetlandhas been attached increasing significance with the merits of low cost，goodpurification effect and high ornamental value. It’s an effective method toinhibit the water eutrophication by removing the nitrogen in the domesticsewage. The constructed wetland can remove the nitrogen by adsorption,precipitation and transformation. It’s of great importance to carry outresearches about the mechanism of nitrogen removal for domestic sewage inthe constructed wetland, which aimed at improving the efficiency ofdenitrification in the system.The objective of this research is to study the interaction among thewetland plants, seasons and the denitrification microorganism, which mayhave an influence on the effect of denitrification for domestic sewage in theconstructed wetland. The influence of temperature and intensity ofnitrification and denitrification on the nitrogen removal efficiency wasanalyzed, and so the possible relationship between the intensity of nitrificationand denitrification. Probe into the study of purification effect and mechanism of denitrification in the integrated constructed wetlands, the main conclusionsare as follows:(1) At the beginning, the effect of the pollutant disposal in the system isnot stable, but it still had a higher efficiency than it reached a steady state. Thesystem had certainly buffering capacity on the pH of the wastewater. Afterrunning steadily, the ratio of TP removal in the system was around57%forthe whole year, and23%,40%for NH4+-N and TN, respectively. The ratio ofCOD removal was relatively steady，which reached the value of88%. Thetreatment efficiency of NO3--N and TP was related to the HRT of the system.(2) The efficiency of pollutant removal in the system was affected by thetemperature; either a high temperature or a low one will reduce the treatmenteffect of the system. In an appropriate temperature range, for example, Juneand September, during which the temperature was rather high and the plantsgrew well, the highest removal ratio of TP and NH4+-N can be up to100%and95%，respectively, and the value for TN and COD both reached70%. Thegrowth of the plants also affected the pollutants removal efficiency of thesystem. Generally, the efficiency of the system during the vigorous growthperiod of the plants had an obvious advantage over the decline period.(3) The biomass variation of Caohai wetland was autumn> summer>spring> autumn, and the size of each sort of plant biomass was Acoruscalamus> Zizania latifolia> Scirpus validus Vahl> Canna indica. Thenitrogen and phosphorus of four plants content hardly change with the seasons. The nitrogen content of four wetland plants showed that Cannaindica> Acorus calamus> Scirpus validus Vahl> Zizania latifolia, plantphosphorus content showed Scirpus validus Vahl> Canna indica> Acoruscalamus> Zizania latifolia. The nitrogen and phosphorus of abovegroundportion contented greater than the underground levels of nitrogen andphosphorus. Through changes in biomass and pollutant removal of fourseason’s comparison, total biomass is the largest fall, and the removal ofvarious pollutants in the fall also reached the highest value. This showsthat the biomass plant still has some influence on the pollutant removalof artificial wetlands.(4) There was no obvious correlation between rhizosphere microbialquantity and pollutant removal of Caohai constructed wetland wetland;Nitrification/denitrification intensity and TN removal rate wassignificantly negatively correlated. |
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