Purificatio Function And Mechanism Of Aquatic And Terrestrial Plants On Wastewater Pollutants

Dissolved oxygen content is an important environmental factor that determines the purification pathway and rate of pollutants in water,especially oxygen consuming organic matterial.Water-Oxygen exchange at the atmospheric interface and oxygen secretion from aquatic plants are the main ways to obtain dissolved oxygen in poorly fluid waters.In previous studies,little understanding was given to the oxygen secretion function of aquatic plants.The terrestrial plant system is an important potential ecosystem for solving the closed water of the park in the future,but at present there is a lack of understanding of the sewage adaptability and pollutant purification function of terrestrial plants.In this study,the aquatic plant hydroponic test and the terrestrial-aquatic plant combined subsurface flow constructed wetland experiment were carried out to investigate the purification functions of common aquatic and terrestrial plants on water-consuming oxygen,organic matter,nitrogen and phosphorus,and the removal of oxygen and pollutants from aquatic plants.Interrelationships,etc.The main research progress is as follows:1.The water aeration effect of three kinds of water-falling aeration methods,such as step flow,waterfall flow and slope flow,is studied.The results show that under the same height(3m),the efficiency of step-flow water-reducing oxygen is the highest,compared with the control water.The sample height is 1.98mg/L,followed by the slope flow,which is 0.58mg/L higher than the control,and the waterfall water drop is the lowest,which is 0.20mg/L.2.The results of hydroponic experiment of aquatic plants showed that:(1)Canna indica,Vallisneria natan and Eichhornia crassipes have the best removal rate of total nitrogen(TN)by more than 95%;Canna indica,Eichhornia crassipes and Cyperus alternifolius have the best removal effect on total phosphorus(TP),and the removal rate is over 70%;Ceratophyllum demersum,Eichhornia crassipes and Canna indica the removal rate of nitrate nitrogen(NO3--N)is better than 95%;The removal effect of ammonia nitrogen(NH4+-N)by Vallisneria natans,Thalia dealbata.and Eichhornia crassipes is better,and the removal rate is over 95%.(2)NH4+-N and TP had close relationship with pH,and the correlation coefficients were 0.344(p<0.05,n=36)and 0.708(p<0.01,n=36),indicating that TP has a greater influence on pH;the correlation between the oxygen secretion rate of plant roots and the removal of oxygen-consuming organic matter in water is higher,and the correlation coefficient is as high as 0.845(p<0.01).(3)It can be calculated by measuring the change of dissolved oxygen(DO)and chemical oxygen demand(COD)in water.The oxygen secretion of the roots of aquatic plants.The oxygen secretion capacity of different plants is different.The oxygen supply capacity of Arundo donax var.versicolor,Thalia dealbata and Cyperus alternifoliusis significantly greater than that of other plants.3.Purify the water by constructing a three-stage subsurface wetland with different plant combinations.Comparing the purification efficiency of the same level wetland plant unit,The results of the study showed that the removal of various forms of N in the Acorus calamus Linn was always significantly higher than that of Hibiscus rosa-sinensis Linn,the TP removal effect was reversed,and the COD removal rate was not much different,between 40%and 44;The removal of various forms of Zoysia matrella is always higher than that of Canna indic.Ficus microcarpa the removal rate of NO3--N,was lower than that of Canna indica.The removal rate of other water quality indicators was higher than that of Canna indica.The TP removal rate of the three plant wetlands of Ficus microcarpa,Zoysia matrella and Canna indica was not significant.There was no significant difference in COD removal rates between Canna indica and Zoysia matrella.Comparing the water purification effects of different plant wetland combinations,the test shows that the combined AEC three-stage subsurface wetland is the best plant combination with the average removal rate of NH4+-N,NO3--N,TN and COD pollutants,and the combined DEC wetland is the average removal of TP pollutants.The best plant combination.The optimal hydraulic retention time of different wetland combinations was compared.The optimal hydraulic retention time of NH4+-N and TN average removal rate was 36h,and the optimal hydraulic retention time of NO3--N average removal rate was 12h.The optimal hydraulic retention time is 24 h,and the average removal rate of TP for the three hydraulic retention times is not much different,ranging from 81%to 84%.In summary,the use of plants and different measures to achieve the purpose of water aeration,improve the microbial degradation rate of oxygen-consuming organic matter in water,combined with the difference in the purification effect of different plants on polluted water,fully consider the problem of plant wintering,select suitable aquatic plants and land Plants planted in constructed wetlands,explored a set of better closed black odor water purification measures,and provided reference for the establishment of an ecological engineering technology application demand for low-cost construction and operation of small closed water bodies.