Study On The Effect Of Sewage Purification In Constructed Wetland Of Lotus Roots And Its Comprehensive Evaluation

In recent years, with the over-exploitation of underground water in northern China, the sewage irrigation, which contains toxic substances and heave metals, becomes quite common. Thus, resulting in lotus roots and soil be contaminated, during the process of purification of sewage by constructed wetland of lotus roots. This research mainly study the mechanism of artificial processing sewage and the correlation between artificial wetland ecosystem and food safety, and provide theoretical basis and practical technical information for the further design and research of wetland systems to purify sewage.The study area is artificial wetlands of lotus in Baoding of Hebei. This research provides a basis for pollution remediation, soil environmental quality assessment and sustainable development and utilization and maintenance of ecological balance studies by studying the soil, water, lotus root, and lotus root leaves of artificial wetlands of lotus ; and making cumulative evaluation /pollution assessment /the potential ecologicalrisk assessment,of soil heavy metal , The main results are as follows:1. The sewage feature of lotus artificial wetlands are low concentration of organic pollutants and higher concentration of nitrogen and phosphorus and suspended pollutants.There is a good treatment effect for purifing sewage by lotus artificial wetlands; the removal rate for COD、TN、NH3+-N、TP、SS respectively are 25.9%-57.1%,38.3%-69.7%,45.4%-49.2%,32.3%-47.9%,62.5%-88.5%.2. Different proportions of nitrogen and phosphate can play a different promoting role in increasing the production of lotus;for example, N3P3 can get a high yield of 39296 kg/hm2, the second is N4P4,is 35779 kg/hm2; and in natural state ,the yield is 22622 kg/hm2; Compared with the control sample, the production increased by 11.4%~73.7% after the fertilization treatments.3. The content of Cd in sewage is 0.037 mg/L, which is 3.7 times of the national irrigation water quality standards for vegetable crops; the content of Zn、Cr, very low, belong to the light pollution of the appropriate water quality classification standards; the comprehensive pollution index of water polluted by heavy metal is 1.59, belong to light pollution.4. Different criteria corresponds to different single factor index of heavy metal,for the pollution index of Cd and Cu,which contained in the 0-20cm soil of lotus artificial wetlands, respectively are 1.372 and 0.338; also, there is a common, the content of Cd is very high ,although under the different criteria. Use national secondary standard and local soil background value as evaluation criteria,the the comprehensive pollution index respectively are 0.2 and 1.12.5. The leaf of lotus root has different enrichment ability for different heavy metal, the order is Cd>Hg>Zn>Pb>Cu>As>Cr; the average enrichment cofficient for Cd/Hg/Cr respectively are 2.33/1.22/0.01.6. The order for single factor pollution index of lotus root is Cd>Zn>Hg>Cr>As>Pb>Cu; there is a high accumulation ability,to heavy metals, for lotus root,which showed by the value (1.22) of comprehensive pollution index .