| This study based on the subject "wetlands continuous purification of tail water from the sewage treatment plant" topics in the topic "Water environment improvement technology research and comprehensive demonstration sub-project of ecological corridor in Pu River", which the part of the key program of national "12th five-year plan"—"The water pollution control of Hun River’s middle stream and comprehensive water environment improvement technology integration and demonstration subject". To the present situation of the tail water from the sewage treatment plant is that, the nitrogen is in high level and the C/N is relatively low, we choose the artificial wetland treatment technology for depth treatment, but the amount of carbon source is the most important limiting factor of the nitrogen removal efficiency, so by the way of adding external carbon source to strengthen nitrogen removal of wetland is imperative. We choose the subsurface-flow and tidal-flow artificial wetlands to be the object of study, use the alkali-heated, acid-alkali-heated corn stalk and special process treated sludge which is from the Shenyang Zhenxing sludge disposal plant, as the solid carbon source, by By artificially simulating the tail water from the sewage treatment plant, research the purification effect two kinds of artificial wetlands. Through the research on each tidal-flow constructed wetland purification mechanism of pollutants in different time and different space, the amount of carbon source can be further determined. Then research the operation effect under this addition. At last fit tidal flow unit’s denitrification kinetics, then compare the denitrification rate of different solid carbon source.Through the static release indicate that the cumulative carbon-nitrogen ratio of alkali-treated corn stalks and special process treated sludge is27.3,8.4; the average daily release amount of carbon element is10.31mg,8.98mg; it average daily release amount of nitrogen element is0.20mg,0.21mg. Through the three-dimensional fluorescence spectrum of two kinds of solid leaching solution, it can be seen that the content of small organic molecules available for microorganism in alkali-treated corn stalks is higher. According to the formula and related literature, we sure to add150g carbon source in these devices make the system c/n increased from4to5.By monitoring these devices various pollutants removal efficiency who added150g solid carbon source, after adding150g carbon source,nitrogen removal rate was raised, but the increase is not obvious. Add150g carbon source in the device to complement the lack of carbon nitrogen ratio, it make the system to raise c/n5:1in theory, but the internal system of c/n is not5:1in actual. Without adding carbon source of tidal flow system with the minimum of artificial wetland D position c/n is only1in the late reaction. In order to improve the low c/n to the5:1in wetland, increase the amount of carbon source to450g.Through the monitoring result of total nitrogen, ammonia, nitrate, nitrite after adding450g carbon source, after adding450g alkali treated corn stalk solid carbon source, the tidal-flow constructed wetland’s TN removal rate increases40%, the subsurface-flow wetland increases32%. After adding450g solid carbon source, there is significant improvement to the removal effect on NH4+-N, it increases about10%, the removal rate of two kinds of solid carbon source shows little difference.In the case of being added450g alkali-treated corn stalk, special process treated sludge solid carbon source, NO3-N removal rate of tidal-flow constructed wetlands respectively increases by27%,10%, while the removal rate of subsurface-flow constructed wetlands respectively increases13%,10%compared to the reactor without carbon source. In the addition of being added450g alkali-treated corn stalk, special process treated sludge solid carbon source, the NO2--N removal rate of tidal-flow constructed wetlands respectively increases27%,21%. Meanwhile the removal rate of subsurface-flow constructed wetlands is respectively55%,47%higher than the reactor which is not added carbon source. Increase the amount of carbon source added no bring burden system of COD removal.When it comes to the removal amount of COD, NH4+-N, NO2--N, TN, the underlayer of the tidal-flow constructed wetlands gravel bed is the lowest,and the second is the upper layer of stromal bed, the middle layer is the highest. But the removal to NO3--N mainly happens in the underlayer which is followed by the middle layer, and the removal rate of the upper layer is lower. The concentration of all kinds of pollutants in subsurface-flow constructed wetlands show a decreasing trend along water flow direction. It is because the carbon source is added in the bottom, water flows from bottom to top, it can provide available carbon source for the denitrifying microorganisms, thus reinforcing the denitrification. Through nitrate nitrogen removal effect of tidal flow unit fitting found that nitrate removal pseudo-first-order kinetic model. It can be seen that the denitrification rate constant kT of tidal-flow constructed wetland which is added450g alkali-treated corn stalk, is2.12times that of the reactor without carbon source, and it is1.28times that of the tidal-flow constructed wetland which is added450g special process treated sludge. Corn stalks enhance the denitrification of the wetland system more significantly. However, in the consideration of the solid waste resource reuse, adding special process sludge as solid carbon source is feasible.The research results have a high application value for the sewage treatment plant tail water denitrification.As the nitrate contamination of the tail water from the sewage treatment plant and the present situation of water eutrophication, in this study we reinforce the carbon-nitrogen ratio by adding the carbon source to improve wetland denitrification capability, and strive to solve the problem at the source, which has broad application prospects in the field of wastewater treatment. |
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