Study On The Strengthening Nitrification In Subsurface Flow Constructed Wetland

Sewage treatment system in SFCW (Subsurface Flow Constructed Wetland) have advantage in stable outflow water quality, strongly enduring impulsion load, the lower of capital construction cost and running cost, easily maintaining, and aesthetics value. SFCW has already abroad be applied in sewage treatment, agriculture point fountain pollution, surface fountain pollution and the treatment in eutrophication of the water bodies.But, the ability of nitrogen removal in SFCW is sometimes relatively poor. Nitrogen removal in SFCW mainly associates nitrification with denitrification. But ORP in SFCW usually is negative. It is able to satisfy denitrification, and it can't satisfy nitrification. Therefore nitrification is a restrict gene in SFCW's nitrogen removal system. The ability of nitrogen (including organic nitrogen) is restricting with nitration.Changed waterpower grade, clearance inflow and aeration inflow were adopted to increase nitrification. The thesis emphasized a modified constructed subsurface wetland that called Wavy Subsurface Flow Constructed Wetland (W-SFCW).The results of monitoring for a year indicated that when the concentrations of influent are:⑴When reducing outflow water level, aerobic area in SFCW is largerer, the ability of nitrification was increasing. Concentration of NH4+-N in W-SFCW's outflow is 8.58mg/L. Average removal rates of NH4+-N in W-SFCW were 78.27%. It heightens 7.51%. Nitrifying activity is increased to 0.49ugN/(h×g) from 0.33ugN/(h×g), it heightens 46.29%.⑵When adopting clearance inflow technic, air enter into the wetland's inner, oxygen covering would be happened in exiguity hole in medium. The ability of nitrification was increasing. Therefore nitrogen in sewage will be easily wiped off. Concentration of NH4+-N in W-SFCW's outflow is 10.37mg/L. Average removal rates of NH4+-N in W-SFCW were 77.56%. It heightens 6.80%. Nitrifying activity is increased to 0.48ugN/(h×g) from 0.33ugN/(h×g), it heightens 45.45%.⑶When adopting aeration inflow, we are ventilating in service reservoir. More oxygen is entered into the wetland's inner, which makes up the limitation that oxygen covering area and the root system's giving out oxygen area are small. It advances nitration reaction. Concentration of NH4+-N in W-SFCW's outflow is 6.53mg/L.Average removal rates of NH3-N in W-SFCW were 85.67%, it heightens 14.91%. Nitrifying activity is increased to 0.55ugN/(h×g) from 0.33ugN/(h×g), it heightens 66.67%.⑷When adopting the technic of reducing outflow water level, clearance inflow and aeration inflow, denitrifying activity reduces a little in W-SFCW. Whereas from macroscopical direction, denitrifying activity is bigger than nitrifying activity, the ability of denitrification is relatively surplus.⑸We synthetically estimate the three techincs of changing outflow water level, clearance inflow and aeration inflow, an cvaluating indicator set used for the decision course to select the techincs was proposed. This will be helpful to use the knowlcdgc of fuzzy mathc mastics to establish the valuating standard and quantification mcthod, and to optimize the decision from candidates by gray associated analysis. According to the estimate result, we know that the techinc of changing outflow water level is the best, and then is aeration inflowt technic; the feasibility of clearance inflow is relatively low.The thesis brought a matter to a speedy conclusion that the data and fruits of this thesis are benefit to the balance of nitrification and denitrification in constructed wetlands'interior.