Study On Enhanced Nitrogen Removal In Compound Constructed Wetland

This paper conducts research on the problems of raw water treatment and effluent purification in Zhongpai Wastewater Treatment Plant.The first-stage pilot test is designed as a multi-media membrane bioreaction unit+composite artificial wetland combination technology to treat raw water from the wastewater treatment plant;the second-stage micro-aerated vertical flow wetland?HFCW?+horizontal subsurface flow wetland?HFCW?+enhanced by carbon source+The submerged plant oxidation pond?SOP?composite wetland process is used for deep purification of wastewater treatment plant effluent;from four types of cyanobacterial materials carbon source and PHB,PBAT,PBSA,PHBV,PSVH material carbon source and purchased PCL carbon source,Through a small trial test,the carbon source with the best denitrification and denitrification effect,suitable carbon supply capacity,long release time,and no secondary pollution of water body will be selected.Through the pilot test research of carbon source parameter optimization,the optimal operating parameters of the best carbon source are determined.This carbon source is used in the two-stage pilot plant with the optimized dosage ratio and operation mode to study the effect of the enhanced composite wetland process on the removal of nitrogen from sewage.The following conclusions are obtained:?1?The one-stage process shows a certain purification effect on the raw water of the sewage plant.The average removal rate of SS for the entire system is 78.24%;the average removal rate of COD_Cris 55.7%;the average removal rate of NH₄⁺-N,TN,and TP is 61.77%,23.08%,and 35.07%.?2?Comparing the advantages and disadvantages of the four carbon sources prepared using cyanobacteria as raw materials and the X-Nitro denitrification carbon source whose main component is polycaprolactone?PCL?,the study found that the enhanced cyanobacteria carbon source enhanced the denitrification capacity of wetlands,but It will cause the concentration of TP and COD_Crin the effluent to increase rapidly,and the addition of PCL carbon source wetland not only has a good denitrification and denitrification effect,but also does not cause secondary pollution of the effluent.Then through the pilot test research on the advantages and disadvantages of PHB,PBAT,PBSA,PHBV,PSVH new material carbon source and PCL carbon source,it was found that the PHBV and PCL carbon source enhanced wetland denitrification effect is better.However,the addition of PHBV carbon source will increase the concentration of COD_Crin the effluent.With the passage of time,the PHBV carbon source will melt and form a viscous substance at the outlet,and the denitrification effect will gradually deteriorate and it will lead to clogging of the wetland matrix.To sum up,it is best to select the PCL material carbon source for the horizontal submerged wetland in the enhanced pilot test.?3?Through the pilot test of PCL carbon source dosing parameter optimization,it was found that the optimal dosing ratio of PCL denitrification solid-state slow-release carbon source and matrix was 10.19g·L^-1;the best dosing method was the mixing of carbon source and matrix Adding;when the hydraulic retention time is about 40h,the removal rate of TN in the wetland reaches 65.54%.?4?In the two-stage pilot test,the effluent from the wastewater treatment plant was further treated by the PCL carbon source-enhanced composite wetland process system.The test results showed that the average temperature of each unit was about 28?,and the UFCW unit had an aeration rate of 1.5m³·h^-1·m^-2,under the condition that the average hydraulic retention time of HFCW unit is 1.03d,the composite wetland process as a whole shows a good purification effect,and the total average removal rate of the system for TN,NH₄⁺-N,TP,COD_Crand SS is 82.5%,53.5%,63.4%,36.5%and 85.3%,of which,the average concentration of effluent TN,NH₄⁺-N,TP,COD_Crand SS is 1.42,0.2,0.15,22.7 and 7.1mg·L^-1,and the sewage treatment plant has been realized The tail water is raised to the goal of the surface IV standard?GB3838-2002?.