Study Of Water Purification Of Aquatic Plant Species In Different Seasons Under Fe-C Interior Electrolytic Substrates

Abstract:In order to improve the purification efficiency of constructed wetland,this study selected the common aquatic plants in wetland ecosystem as the research object,and built small scale experimental apparatus with iron-carbon interior electrolytic substrates as the matrix.The concentration change of water quality indexwas used as the characterization factor.The purification effects of sewage were studied under different seasons,different experimental time,different plants and their combinations,aimed to provide optimum plant configuration for rivers of different levels of pollutants.To compare water purification of common aquatic plants under iron-carbon interior electrolytic substrates in summer,four common aquatic plant species Eichhornia crassipes,Nymphaea tetragona,Acorus calamus and Phragmites australis were used as study species.The effect of sewage COD,ammonia nitrogen,TP content under different experimental time(1-5 d)among aquatic plants under iron-carbon interior electrolytic substrates were analyzed in small scale experimental apparatus.The experiments were conducted in two batches.The experimental water quality index was based on the field survey data in April 2015.To compare water purification of aquatic plants under iron-carbon interior electrolytic substrates in winter,three aquatic plant species Elodea nuttallii,Oenanthe javanica,Iris sibirica were used asstudy species.Six processing and a control group were added sewage.To compare the plants growth condition in sewage,setting up three single-plant groups with clean water in the meantime,the chlorophyll content of three kinds of plants were measured to compare the growth status of the plants in sewage.The effect of sewage COD,ammonia nitrogen,total nitrogen TP content under different experimental time(1-5 d)among aquatic plants under iron-carbon interior electrolytic substrates were analyzed in small scale experimental apparatus.The experimental water quality index was based on the field survey data in October 2015.Due to the low temperature in the second experiment,nitrogen purification effect was poor in experimental system,so the third experiment was done indoors with air conditioner improving the temperature.To compare water purification of common aquatic plants under iron-carbon interior electrolytic substrates in winter indoors,four common aquatic plant species A.calamus,I.sibirica,Ceratophyllum demersum,Myriophyllum spicatum were chosen.The effect of sewage COD,ammonia nitrogen,total nitrogen TP content under different experimental time(1-11 d)among aquatic plants under iron-carbon interior electrolytic substrates were analyzed in small scale experimental apparatus.The experimental water quality index was based on the field survey data in August 2016.The results showed that:In summer experiment,single aquatic-plant could effectively remove ammonia nitrogen,COD,TP compared with no-plant control group.But the efficiencies were significantly different among different species.Ammonia nitrogen removal rated up to 100%in E.crassipes with the processing sewage for two days,and A.calamus in three days.Each plant combination had good removal rate of ammonia nitrogen.Concentration of COD in E.crassipes approached zero with processing sewage for three days,A.calamus second.The concentration of COD in combination of E.crassipes and A.calamus water reduced to a minimum of 4.33 mg/L with the removal rate of 85.1%.The concentration of TP was the lowest in E.crassipes with processing sewage for four days,P.australis second.The lowest concentration of TP was in combination of E.crassipes and A.calamus with processing sewage for two days.The combination effect of interior electrolyte and plant is better than that of pure interior electrolyte on the purification of sewage.Plant configuration should be optimized according to the level of pollutants.In winter outdoor experiment,different plants and their combinations have different effects on pollutants from summer,especially ammonia nitrogen.Compared to summer,the purification effect of COD by plants was relatively slow.COD concentration in each group for five days was similar to that of the first day in summer experiment.In addition to control group,other treatments were better for the purification of COD.And the combination of I.sibirica and E.nuttallii,had the best purification effect.Ammonia nitrogen rose at different levels after two days.The concentration of TN showed a decreasing tendency at two days,among which the concentration of TN was the lowest and the purification effect was better in O.javanica group and the combination of I.sibirica and O.javanica.Then there was a rising trend of volatility.All treatments had good effect of TP purification.In this experiment,all treatments did not have a significant effect for nitrogen purification,suitable aquatic plants having good purification effect for nitrogen in winter should be continued to select.In winter indoor experiment,compared with the second experiment,the experimental environment changed,the temperature increased.Ammonia and TN purification effect had improved,especially TN purification effect was relatively better.Concentration of TN was lowest with A.calamus under nine days,the combination of C.demersum and M.spicatum second.The purification effect of COD and TP was also good and very stable during the experimental period.The concentration of COD in each system was lowest at seventh day.The COD concentrations of control group and C.demersum were lowest.The substrate was good for the purification of COD and TP,and the removal of ammonia nitrogen and TN were relatively poor.