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Based on the small trial of tidal flow artificial wetland, alkali-treated corn straw is used as carbon source supplement for denitrification. The author studys the effect of adding different amount of carbon source on removal efficiency of TN, NH4-N, NO3-N, NO2-N and COD in the system. The results of the study show that: when the adding amount of alkaline straw are 0, 100g and 400g, NH4-N average removal efficiency are respectively 59.9%, 66.96% and 71.91%; NO3-N average removal efficiency are respectively 54.89%, 72.33% and 81.36%; NO2-N average removal efficiency are respectively 12.76%, 24.91% and 40.97%; TN average removal efficiency are respectively 23.14%, 41.32% and 64%; COD average removal efficiency are respectively 83.94%, 81.29% and 77.85%. Alkali-treated corn straw can provide the carbon source that denitrification required for artificial wetland system. The added carbon source can significantly improve the nitrogen removal efficiency of the system, and the nitrogen removal efficiency of adding 400g alkali-treated corn straw is better than adding 100g alkali-treated corn straw, and it is not a burden for the system. Introduction Artificial wetland is a ecological sewage purification technology which designed and built by people through simulating natural wetland with the features of controllable and engineering. And it can effectively remove organic pollutants in the polluted water. At present, it has been widely used to treat disperse wastewater with middle and low concentration at home and abroad. The research shows that the main limiting factor for denitrification is carbon source in artificial wetland which was used for nitrogen removal, and adding exogenous carbon source can effectively improve the wetland’s nitrogen removal efficiency. At present, most domestic and foreign scholars solve the problem of insufficient carbon source by adding liquid organic carbon to influent, such as glucose. But the liquid carbon source have the problem of serious loss with flow and low utilization rate, these need to be further researched. In the study, using wastewater by laboratory preparation simulated tidal flow artificial wetland. Meanwhile, alkali-treated corn straw is added as plus carbon source with the no external carbon source as the blank contrast. Under the same conditions of influent water quality, the author studied the effect of adding different amount of carbon source on removal efficiency of TN, NH4-N, NO3-N, NO2-N and COD in the tidal flow artificial wetland to provide the reference for further research and design of artificial wetland wastewater treatment. Experiment materials and methods Experiment operating conditions. Small scale artificial wetland system consists of tidal flow artificial wetland units. The 3 sets of experiment device respectively is: No. 1 device that is tidal flow artificial wetland blank contrast; No. 2 device that is tidal flow artificial wetland added 100g alkaline corn straw; No 3 device that is tidal flow artificial wetland added 400g alkaline corn straw. The influent is controlled by peristaltic pump and PCL time controller in each unit. Each device is International Power, Electronics and Materials Engineering Conference (IPEMEC 2015) © 2015. The authors Published by Atlantis Press 477 made of organic glass cylinder with the diameter of 30cm, the height of 85cm and the total volume of 45L. In the device, the height of filler is 70cm (at bottom the diameter of filler is 20~50mm and the thickness of gravel layer is 15cm; at middle the diameter of filler is 8~15mm and the thickness of gravel layer is 20cm; at the upper the diameter of filler is 3~5mm and the thickness of gravel layer is 35cm). The 15cm-thick filler at bottom is used for drainage layer. The reserved 10cm-thick filler at cylinder upper is used for influent distribution area. In addition, the extra high of 5cm is set at the top. Experiment device as shown in figure 1. Fig.1 Schematic diagram of the experiment device Experiment materials. In the experiment, the handles of corn straw selected plus carbon source are as follows: washing the corn straw to remove dust; drying for two hours with 108°C; cutting it short to approximately 1cm length and longitudinally cut into appropriate size; constant temperature water bath heating 1h with 90°C in 1% NaOH solution; rinsing it tap water; drying to constant weight and cooling in the oven; then putting it into the sample bag and letting it stay in the dryer as spare. System operating conditions. The system’s influent use artificial simulated sewage that is prepared by glucose, ammonium chloride, potassium dihydrogen phosphate, sodium nitrate, sodium nitrite, and other drugs as trace elements’ supplement, such as CaCl2·2H2O, MgSO4·7H2O, FeSO4·7H2O and so on. When the devices are stable, collecting the influent and effluent water samples to monitor the water quality indexes of TN, NH4-N, NO3-N, NO2-N and COD. No. 1 device don’t add any material, No. 2 and 3 device respectively adds 100g and 400g alkaline crop straw, which both add at the bottom. Unit operating mode is: influentreaction period (3h) drainageidle period (3h), and each period last 6h. Main monitoring index and method. In the experiment, main monitoring water quality indexes include TN, NH4-N, NO3-N, NO2-N, COD and pH. Among them, CODCr uses the rapid digestion method, pH value uses the glass electrode method, NH4-N uses Nessler's reagent spectrophotometry, NO3-N uses UV spectrophotometry, NO2-N uses N-(1-naphthyl) ethylenediamine spectrophotometry, and TN uses Potassium persulfate digestion UV spectrophotometry. Results and discussion NH4-N removal efficiency in each reactor. When the influent NH4-N average concentration is 12.25mg/L, the effluent NH4-N average removal rates in 3 devices as shown in figure 2. From figure 2, we can see that the effluent NH4-N average removal rates of 1, 2 and 3 artificial wetlands are 59.9%, 66.96%, 71.91%. The NH4-N average removal rates from high to low: No.3 device >No.2 device >No.1 device, the effluent NH4-N removal rate of adding 400g alkali-treated corn straw is highest. In the whole experiment, the NH4-N removal rate of No.3 device is the 15% higher than that without adding alkali-treated corn straw device, which may be due to adding alkali-treated corn straw can provide the absorption and utilization of the carbon source for microorganisms growth, and promote the NH4-N removal, the available carbon source provided for No.3 device is more than No.2 device, so the NH4-N removal rate of No.3 device is higher than No.2 device. Thus, adding alkali-treated corn straw is conducive to the tidal flow constructed

The Effect of Adding Different Amount of Carbon Source on the Nitrogen Removal Efficiency of Tidal Flow Artificial Wetland