Research On Water Quality Improvement Technology Of Hongze Lake Reserve Water Source

The backup water source of Hongze Lake adopts a composite constructed wetland system for water quality purification.This paper monitors the water quality indicators and water ecological changes of each treatment unit in the water source through field experiments,and mainly studies the overall change trend of the water quality of the backup water source and each treatment area.The effect of water quality improvement,and the analysis of the changing laws of the artificial wetland ecosystem in the alternate water source area,to provide later management suggestions for the pollution prevention and management of the alternate water source area.Mainly include the following:(1)Through field experiments,the overall effectiveness of the improvement of the water quality of the standby water source was studied,and the seasonal change trend of the water quality of the standby water source was explored.The results show that in the alternate water source,the removal rate of CODMn is the highest in summer(July,August,September),with an average removal rate of 32.24%,and the removal rate is low from November to April of the following year.The average removal rate is Only 16.9%.The turbidity of the water outlet has dropped significantly,the turbidity value is between 3.79-20.22NTU,slightly higher from August to January,lower from March to July,the removal rate is the highest in July,the removal rate can reach 97.13%,and it is removed in December The lowest rate,the removal rate is 66.53%.The overall removal rate of TN is relatively high,ranging from 40.77%to 70.94%,high in summer and low in winter,and the removal rate from April to December is greater than 50%.The average value of ammonia nitrogen at the outlet is 0.29～0.73mg/L,and the change trend is the same as that of the inlet water.It reaches Class Ⅱ water quality standard from January to July,and reaches Class Ⅲ water quality standard in other months.The overall removal rate is between 9.57%and 35.95%.The overall removal rate of total phosphorus is between 25%and 70.59%.(2)Through field experiments,we studied the water quality improvement effects of six units of alternate water source pretreatment zone,clean water ecological filter wall,composite wetland area 1,composite wetland area 2,composite wetland area 3,and deep water purification area.The results It shows that the composite wet area is the main area to remove CODMn and TP;the pretreatment area,ecological filter wall,composite wet area,and deep water area are the main areas to remove turbidity substances;the ecological filter wall and composite wet area have obvious effects in removing TN;The treatment zone and the compound wet zone are the main areas for removing NH4+-N;the pH value and dissolved oxygen will decrease slightly after entering the reserve water source,and will increase slightly after entering the deep water area;the transparency will be greatly improved in the deep water area.(3)The effect of constructed wetland ecosystem on water quality improvement in backup water source area was studied through on-site monitoring,and the species,density,distribution of aquatic animals and plants,sediment deposition rate and pollutant content in raw water of Hongze Lake in backup water source area throughout the year were investigated.The results show that there are 8 tappets in the backup water source area,which are mainly distributed in the composite wetland area with a total area of 40396.37m2.There are 4 kinds of submerged plants,which are mainly distributed in the flow trough of composite wetland area and 3 m wide on both banks of deep water area with a total area of 26990 m2.There are rhomboid horns and three floating plants(weed,duckweed and water hyacinth),which are mainly distributed in the upstream of deep water area and have a total growth area of 9594.16 m2.The water source area is planted alternately with different plants in different areas to construct ecological system of tappets,submerged plants and floating leaves.There are abundant plant species,which can achieve high efficiency and stable purification effect throughout the year.There are 8 kinds of fishes in the deep water area.The total fish resources are about 29491 kg.The silver carp and Bighead Carp put into the backup water source have good growth,which effectively inhibit the growth and reproduction of cyanobacteria and well realize the transfer of nitrogen and phosphorus in the water body.The annual average sediment thickness of backup water source is 0.9,0.5 and 0.6 cm/year respectively.The sediment deposition rate in backup water source is slow and no need for dredging in short term.