| With the development of graziery, the universalization and the scalization of biogas engineering, the emphasis in our country of biogas slurry disposal is to remove contaminant, to prevent soil and water pollution, and to discharge up to the standard. However, there are many problems in factual biogas slurry processing, such as high concentration of organics and nitrogen, poor biochemical quality, low carbon-nitrogen ratio and so on. The traditional biogas slurry disposal process is anaerobic and aerobic method, with which it cannot reach the standard when discharge. Although further disposal may be processed by physical or chemical way, it always causes increasement of costs and secondary pollution. While constructed wetlands with its low investment and simple management characteristic can just conquer these problems in some degree. So it can be mainly used for biogas slurry disposal, especially in rural area.Biogas slurry is the residual liquid processed by anaerobic digestion of organic, contains lots of chemical oxygen demand, nitrogen and phosphorus, if directly discharge can cause water and soil pollution, need after a series of treatment, can be discharged into the environment. In view of the efficiency advantage of constructed wetland in sewage, the paper intends to introduce the constructed wetland system to biogas slurry late depth processing.By plant cultivation experiments and constructed wetland simulations, the optimum parameters for slurry process were searched out which can be referenced for biogas slurry late depth processing.Researching the adaptability in biogas slurry of seven hydrophytes by hydroponic experiments, the best hydrophytes in disposing COD, TN and TP are respectively evergreen, anthurium and spathiphyllum.Under a certain interval condition, the removal efficiency of COD, TN and TP for each hydrophyte are significantly different. And each plant’s removal rate of COD and TN is higher than the rate of TN. The rate of TN for each plant is basically from60%to90%. The removal rate of TN for evergreen, anthurium and Spathiphyllum is inside70%to90%. Especially at28d, the rate of TN for anthurium reaches the highest level of88.4%. And the removal rates of TP for all three kinds of plants are low. At the28d, evergreen has the best efficiency of58.6%.The advisable HRT of evergreen, anthurium and spathiphyllum wetland systems is seven day. The disposal efficiency of these three systems is all have a tendency of increasing first and then decreasing. As the HRT is7d, evergreen system reach the highest removal rate of TN of89.45%, and anthurium has the optimum removal efficiency of COD of88.91%, and the removal rate of TP for spathiphyllum is78.99%.The advisable influent COD concentration of evergreen, anthurium and spathiphyllum wetland systems is200to300mg/L.Under the low water concentration, influent COD concentration of100to200mg/L, evergreen and spathiphyllum wetland system has the optimum final removal efficiency of TP,85.33%and73.39%respectively. Anthurium wetland system has the optimum final removal efficiency of COD,85.61%. Under the medium water concentration, influent COD concentration of200to300mg/L, evergreen wetland system has the optimum final removal efficiency of COD and TN,83.19%and88.54%respectively. Anthurium wetland system has the optimum final removal efficiency of TN and TP,85.96%and83.02%respectively. And spathiphyllum wetland system has the optimum final removal efficiency of TN and COD,79.27%and76.72%respectively. Under the hige water concentration, influent COD concentration of300to400mg/L, evergreen anthurium and spathiphyllum wetland systems are all have the optimum final removal efficiency of COD,78.79%,72.01%and73.58%respectively. Overall, the higher the concentration is, the better the efficiency is.The advisable matrix of evergreen, anthurium and spathiphyllum wetland systems is crushed stone. In the same hydrophyte wetland system, the removal efficiency of crushed stone matrix is better than gravel system. In the crushed stone system, the highest removal efficiency of COD, TN and TP for evergreen are respectively74.62%,78.70%,86.13%. Anthurium system is72.02%,72.44%,80.21%. And spathiphyllum system is72.79%,73.88%,82.82%. In the gravel system, the highest removal efficiency of COD, TN and TP for evergreen are respectively72.14%,75.54%,82.04%. Anthurium system is72.02%,72.44%,80.21%. And spathiphyllum system is70.05%,72.73%,81.23%.The efficiencies are different between different hydrophytes configurations. The mixture of evergreen and anthurium has the disposal rates for COD, TN and TP,78.62%,73.70%and72.21%respectively. The mixture of evergreen and spathiphyllum has the disposal rates78.62%,73.70%,72.21%respectively. The mixture of anthurium and spathiphyllum has the disposal rates69.24%,71.63%,69.84%respectively. The mixture of evergreen anthurium and spathiphyllum has the disposal rates69.24%,71.63%,69.84%respectively. The best disposal rate for COD is the mixture of evergreen and anthurium, which reaches78.62%. And the best disposal rates for TN and TP are both the mixture of evergreen anthurium and spathiphyllum, which reach75.54%and 73.08%. |
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