Experimental Study On Purification Of Fuhe River By Horizontal Subsurface Flow Constructed Wetland

Baiyangdian was classified as the“New Three Lakes”water pollution control system in 2017,and Baiyangdian ecological environment management entered a new stage.It is expected that the water quality of Baiyangdian Lake will gradually return to the Class III-IV water body standard in the middle of this century.Fuhe River is one of the tributaries of water flowing into the Baiyangdian River all year round.Its water quality is of great significance to the Baiyangdian water environment and the construction of Xiong’an New District.Investigate and purification technology research on the water environment of the Fuhe River,with a view to providing reference for the Baiyangdian watershed management.The water quality in Fuhe River city section of baoding city was investigated and analyzed.According to the characteristics of water quality in Fuhe River,the screening test of wetland plants was carried out to compare the removal effect of plants on pollutants in water and select the plants with better effect by combining with the local growth environment.The simulation test equipment of constructed wetlands for horizontal subsurface flow was constructed,and the optimal operating condition was determined by comparing the removal effect of wetlands on pollutants under different operating conditions;The purification effect of wetland system operating under optimal conditions on Fuhe River was analyzed,and the concentration of pollutants in the system was simulated by Mathlab software,and the variation rules of pollutants in horizontal and vertical directions were analyzed.Four typical sections of Fuhe River city section were selected for investigation.Test its water quality,analysis shows that the chemical oxygen demand（COD）,total phosphorus（TP）and ammonia nitrogen（NH₄⁺-N）in the river water generally show a regularity in the flat water period is greater than in the high water period.Fu River has poor water quality and is inferior to V-type water bodies.According to the combination of different plants（phragmites australis,iris pseudacorus L,cyperus alternifolius）and different fillers（ceramicite,crushed stone）,8 groups of comparative simulation test devices（size:650 mm×350 mm×400 mm）were designed.The influent water is taken from the section of Yonghua Bridge on Fuhe River,and continuous operation test is carried out,test results show that the cyperus alternifolius has the best purification effect on COD and TP,and phragmites australis have the best effect on the purification of NH₄⁺-N in water.Two sets of simulation test devices with dimensions of 1200 mm×600mm×800 mm were constructed.nine effective sampling ports were designed along the flow direction of the device and fill ceramsite and gravel respectively,wetland plants for reed,water from the Yonghua bridge section,continuous water.When the test device is operated under the condition of hydraulic load of 0.2 m³/（m²·d）,the system has the best purification effect on Fuhe River water.The content of COD,TP and NH₄⁺-N in the effluent of the ceramsite wetland test device reaches the IV water body standard,which is slightly better than the gravel wetland system.The first-order kinetic model can well describe the removal of COD,TP and NH₄⁺-N by two systems;The COD,TP and NH₄⁺-N in the ceramsite wetland trough and the gravel wetland trough are mainly removed in the first 1/3 of the system,and the removal rate increases along the path.The study found that the horizontal subsurface flow constructed wetland system has a good purification effect on the Fuhe River water in Baoding,and it has reference significance for the application of the system to engineering examples.