Seasonal Variation Of Main Pollution Factors In Xijiu Lake Of Yixing And Removal Characteristics In Extremely Shallow Wetlands

The improvement of water environment in Yixing is of great value to the reduction of the load of Taihu Lake.The city is located in the upper reaches of the Taihu River,is the catchment area of Western rivers into the lake Taihu basin,led by the Yixing city Taihu into the water and pollutant load accounted for about 50% of the total lake,nitrogen and phosphorus and organic waste reduction pressure.The paper was focus on Xijiu Lake,carries on the characteristics of pollutant distribution and analysis on pollution sources of Xijiu Lake in Yixing.The static sedimentation performance of Xijiu water body was analyzed by static experiment of turbid hydrostatic sedimentation,The static sedimentation performance of Xijiu Lake was analyzed by static experiment of turbid hydrostatic sedimentation,analyzed the size grading static sedimentation of suspended solids in the process,and the effect of humic acid on the turbidity of the water was analyzed.The removal efficiency of nitrogen and phosphorus and the pH value of wetland effluent were studied by combining the ratio of phosphorus adsorbent and hydraulic load to study the operating parameters of the superficial subsurface flow constructed wetland,to provide decision basis for the design on pilot-scale of Xijiu Lake.Specific design and research results are as follows:(1)The water quality monitoring data of Xijiu Lake water resources from2013~2015 in Ring Garden and Jiubin Waterworks were collected and analyzed by cluster analysis and factor analysis in multivariate statistical analysis.The results showed that the overall eutrophication was serious,and the mean concentration values of TN and TP were worse than those of the surface water body Grade ?standard.The nitrogen and phosphorus pollution was still the main factor of water pollution in XijiuLake;the mean concentration values of CODMn was Grade III standard,but still The key influencing factors of water pollution;In addition,the water turbidity,the sensory effect is poor,the water transparency is low;the water quality could be divided into 2 typical periods at temporal scale: non-flood season(December to April),flood season(May to November),the quality of non flood season was obviously worse than that in flood season(P<0.01).(2)The turbidity and sedimentation time of the water were poor,and the relationship between the turbidity and the settling time was fitted by Origin 8.1 software.The results show that the turbidity and settling time are exponentially decaying,the correlation coefficient is above 0.97,and the fitting effect is very good.When the turbidity settles about 1/2,the proportion of particulate matter in the range of 4-32 ?m is obviously reduced,the proportion of particulate matter in the range of more than 32 ?m is obviously increased,the concentration of suspended matter decreases significantly,while the organic group The increase was significant,indicating that the correlation between organic matter(humic acid)and turbidity was significant.Furthermore,the correlation between turbidity and humic acid in Yixing city was verified.The results showed that the key influencing factors of river water quality in Yixing city.(3)The ratio of modified hydration cement and broken stone phosphorus adsorbent(1: 9,2: 8,3: 7)had a significant effect on the pH value of wetland effluent.The pH value of the effluent from the wetland system was higher than 9.0 when the ratio of phosphorus absorbent was 3: 7,and the hydraulic load(0.10,0.20,0.30 m3/(m2·d))was higher than that of the wetland The pH value of effluent has a certain influence,with the increase of hydraulic load,the pH value of wetland effluent decreases.(4)The wetlands have a good effect on phosphorus removal.The effect of the ratio of phosphorus adsorbent on the removal of phosphorus from each wetland system is small.With the increase of hydraulic load,the removal of phosphorus from wetland is weakened.At the end of the run,the total phosphorus concentration of the wetland effluent with the hydraulic load of 0.10,0.20 m3/(m2·d)satisfies the surface water body Grade ? standard.(5)The effect of the ratio of phosphorus absorbent on the removal of ammonia nitrogen in the wetland system was small.With the increase of the hydraulic load,theremoval of ammonia nitrogen was weakened.In the later stage of operation,under the three kinds of hydraulic load conditions,the ammonia concentration of effluent from wetland meets the standard of surface water body ?.(6)The effect of phosphorus adsorbent on total nitrogen removal in wetland was lower.With the increase of hydraulic load,the removal of total nitrogen was weakened.In the later stage of operation,under the three kinds of hydraulic load conditions,the total nitrogen concentration of wetland water did not meet the standard of surface water body ?.It is suggested that the latent bed wetland with the depth of 60 cm should be added after the very shallow subsurface constructed wetland,and the aerobic,anoxic or anaerobic environment will be formed,which will be beneficial to the nitrification and denitrification of the wetland.