Study On Purified Efficiency Of Electroplating Wastewater By Wetland Plants In Constructed Wetland

The constructed wetland as land-intensive biological treatment systems has been used in the purification of sewages.The advantages of wetland also include correspondingly low cost,simple operation with stable effluent quality and good resistance to shock loading.It is suitable for China,especially for the domestic wastewater of city.Nowadays attention has focused particularly on the use of constructed wetlands for the treatment of industrial effluents.Macrophyte plays important roles in constructed wetland,not only uptake the pollutants in waste water, maintains constructed wetland's environment,but also possesses economic value and ecological aesthetics value.Lots of toxicants which were always vital items of the environmental analysis were present in the electroplating wastewater.It will do harm to mankind and the environment if the sewage was not treated.A vertical-horizontal subsurface flow constructed wetland was built to treat the electroplating wastewater.In this study,we provide new knowledge about the constructed wetland and the plants,which will be of great help for the environment rehabilitation.The major results and conclusion are summarized as below:1.It studied on the phytopurification and phytoremediation of electroplating heavy metals Cr,Zn,Fe,Mn,Ni and Cu by constructed wetland in Jin Hua.The results showed that this system was a great adaptive system and had a significant removal efficiency of electroplating wastewater.The removal rate of COD,SS was separately above 58%and above 90%.The ability of purification in heavy metals was:Zn＞Cr＞Fe＞Cu＞Ni＞Mn.The results demonstrated that plant assimilation, bacteria degradation and substrate physical chemistry absorption were their main removal pathways.2.Through the analysis of the water,the substrate and plant's tissue in the constructed wetland,it is indicated that heavy metals mainly accumulated in the upper part of the substrate.Lythrum salicaria,Scirpus triqueter,Canna indica growed well and Iris pseudoacorus growed normally in the second wetland,but Phragmites australis nearly stopped growing.Eichhornia crassipes,Echinochloa crusgalli growed slow in the first wetland after 60 days.The phytopurification and phytoremediation by plants differed distinctly with plant species,their parts,their biomass and kinds of metals.Scirpus triqueter,Canna indica had higher capabilities of phytopurification and phytoremediation of electroplating sewage.Eichhornia crassipes had better removel ability than Echinochloa crusgalli.The S/R and BCF value of Zn,Mn,Ni of Scirpus triqueter was higher than 1.The S/R value of Cr,Zn,Ni,Cu of Canna indica was higher than 1 and its BCF value of Zn,Mn was higher than 1. This study showed that the second wetland macrophytes is the better choice,Scirpus triqueter,Iris pseudoacorus,Lythrum salicaria and Canna indica are recommendable better spesies in purifying and remedying the low-medium concentrations electroplating sewage.More strong resistance macrophytes should be applied in the first wetland which had high pollution load.3.Selected high growth plants in constructed wetlands in winter could improve the purification ability of wastewater.Plants couldn't grow normally in constructed wetlands in winter.Solution culture experiment was carried out to characterize differences in tolerance,uptake and accumulation of heavy metals in simulate electroplating water.Results showed that all plants couldn't survive in the highest simulate electroplating waters.Hydrilla verticillata,Oenanthe javanica had no significant differences in plant growing,the growth of Roegneria kamoji was distinctly restrained.Compared to control,TTC of plants decreased significantly except for Acorus gramineus and MDA content of plants increased except for Oenanthe javanica.It indicated the adversity could bring some harm to plants.Meanwhile,the Pro,as well as the SS was more than control except for Roegneria kamoji.It showed they had tolerance in adversity.Concentrations of heavy metals in both species increased with increase of metals in solution.Root of plants accumulated more heavy metals of Cr,Zn,Fe,Mn than shoot,but it was opposite of Ni, Cu.Overall uptake of heavy metals by Oenanthe javanica,Acorus gramineus were more than other plants.To sum up,Oenanthe javanica, Acorus gramineus,Hydrilla verticillata,Juncus effuses were satisfied with the phytopurification and phytoremediation of low-medium concentrations electroplating wastewater in winter. 4.The spectra of root,stem,leaf of Oenanthe javanica with CK,low, medium,high metal treatment(Cr,Fe,Mn,Zn)was determined by Fourier Transform Infrared(FTIR)spectrometry with OMNI-sampler directly,fast and accurately.The results showed:the peak shape of plant component kept invariable basically when absorbed heavy metals. Significant shifts of some functional groups such as hydroxy groups(3328-3361cm^-1),carboxyl groups(1402-1440cm^-1),carhoxamido groups(1620-1645cm^-1)absorption peaks can be seen when they participated in the process of absorbing heavy metals.With strong identifying ability,exact determining results and fast response function, the application of FTIR method has been popularized gradually in the field of environmental science.5.The responds of Alternanthera philoxeroides and Eichnornia crassipes to the wetland polluted by electroplating wastewater which contained heavy metal Gr,Zn,Fe,Mn,Ni and was studied.The effect of two species on the polluted wetland were also studied.The results showed that the two species had good tolerance and can absorb the heavy metals mentioned above in various degrees.The ability of purification in heavy metals was Zn＞Fe＞Cu＞Cr＞Ni＞Mn and Cu＞Zn＞Fe＞Cr＞Mn＞Ni respectively.These purified ability differences between the two species might reflect the biological characters and the physiological changes in plants.Eichnornia crassipes could be suitable for phytopurification and phytoremediation of electroplating wastewater.