Simulation On The Effects Of Organic Load Rate On The Purification Of Integrated Vertical Flow Constructed Wetland

Integrated Vertical Flow Constructed Wetland?IVCW?is a common type of subsurface flow constructed wetland.Due to the influence of its structure,the hydrodynamic characteristics and biochemical reaction of water quality are different and complex in space,and its denitrification capacity is generally better than that of single structure subsurface flow wetland.There are a lot of experimental results in the study of IVCW,but due to its complex structure,the research on its numerical modeling is still blank.In this thesis,the open source multi processes coupling model?Ogs#IPhreeqc?is used to realize the process simulation of IVCW.A series of inversion analysis is carried out around the key index of organic loading rate?OLR?.The main results of this study are summarized as follows:?1?Based on the CWM1 biodynamic module as the biochemical reaction process,three simulation functions,i.e.the attachment-detachment process of particulate pollutants on the medium,the limitation of microbial growth and the release of carbon source from wetland plants,were added to the OGS#IPhreeqc model system;the simulation of the reaeration process of IVCW was modified to simulate the aerobic-anoxic-aerobic process conducive to nitrification-denitrification in IVCW.The calculated water quality index is in good agreement with the measured results.?2?The sensitivity analysis of parameters showed that the simulated water quality indexes of non-bacterial components and bacterial species were sensitive to the organic load?OLR?of IVCW.The results of different OLR input conditions show that too high or too low OLR will weaken the removal ability of IVCW to TN,and with the increase of OLR,the removal rate will decrease rapidly.When the input OLR is in the range of10.8 g m^-3d^-113.0 g m^-3d^-1 and the C/N ratio is in the range of 7.3⁸.8,the better oxidation-reduction conditions can be built in the wetland,so that NH₄-N,TN and chemical oxygen demand?COD?have higher removal rates.?3?Considering the characteristics of outdoor operation of subsurface flow wetland,the simulation results show that the increase of temperature?10?²5??can offset the adverse effects of the increase of OLR.However,when the OLR is too high,even though the temperature regulation,it cannot change the trend of the decline of NH₄-N and TN removal capacity.?4?During the period of organic shock load,the removal capacity of COD,TN and NH₄-N were obviously weakened,and the pollutant effluent concentration reached the peak value before the end of shock loading.The impact of organic shock loading on COD is much smaller than that of TN and nh4-n.And by reducing the impact load and prolonging the impact time,the buffer capacity of COD treatment in the system can be increased to a certain extent.