Study On Re-purification Of Tail Water From Urban Domestic Sewage Treatment Plant By Constructed Wetland

Constructed wetland system is a wastewater treatment technology developed in1980s which involves many aspects,such as physics,chemistry,biology and so on.In this study,we selected the common aquatic plants in Yi River Basin,and studied the effects of floating plants,floating plants,emergent plants and submerged plants on the nutrient purification of water bodies with the method of laboratory culture,and we monitored the adaptability and water purification status of plants in heavy pollution water body,analyzed the purification ability of different plants on eutrophic water,screened out pollution control vegetation used in artificial wetland purification.In the artificial wetland?located in Linyi City,East Timor River into the Yunmeng Lake?planted and screened out plants with certain economic value of pollution control,use the constructed wetland technology to treat tail water discharged from sewage treatment plant,conducted ecological benefit evaluation of wetland treatment system.The results are as follows:?1?static cultivation experiment and pollution control plant screeningAquatic plants have a certain effect on the purification of nitrogen and phosphorus in water.Study on the use of aquatic plants on the removal rate of nutrients in the water.The results showed that the removal rate of ammonia nitrogen was more than 95%,the maximum value of 99.48%,the removal rates of total nitrogen in water body are quite different among various aquatic plants,and the removal rate of total nitrogen by aquatic plants is 23%-90%;In comparison,the removal rate of total phosphorus in water body fluctuates greatly:the minimum value is 14%,the maximum value is 90%.According to the experimental results of water nutrient removal efficiency and the screening results of pollution controlling plants,calamus,iris pseudoacorus,ceratophyllum demersum,scirpus tabernaemontani,typha orientalis presl,canna indica Lin,thalia dealbata,pontederia cordata and lythrum Salicaria 9 kinds of aquatic plants were selected out to provide reference for the establishment of wetland system.?2?the effect of constructed wetland on the removal of nutrients in waterDue to the growth of aquatic plants,the phosphorus removal efficiency of constructed wetlands in water body is relatively high from 31%to 48%in summer and from 31%to 48%in summer.Due to the withered winter plants,the removal efficiency of constructed phosphorus in winter is relatively low,22%-27%.Due to the growth of aquatic plants,the nitrogen removal efficiency of constructed wetland systems is relatively high from June to October in summer,which is 29%-44%.Due to the withering of winter plants,the removal rate of constructed wetlands in winter is relatively low,ranging from 19%to 27%.The removal efficiencies of TN and TP are similar for constructed wetland systems,both in summer and relatively low in winter,which is directly related to the rapid plant growth and mortality.The removal efficiencies of NO₃-N and NH₄⁺-N by constructed wetland systems show that the removal efficiencies of NO3-N in constructed wetland systems are relatively high at 32%and 31%respectively in June and August,and are relatively higher in other months low.In June,the removal efficiency of NH4+-N in constructed wetland system was relatively high at 51%.In the wetland,the total amount of nitrogen and phosphorus accumulation in reeds and cattail increased gradually after August 2016,and reached the maximum in December.In the constructed wetlands,the maximum total nitrogen enrichment of Phragmites australis and Typha was 2.99 t and 3.67 t,respectively.The maximum total phosphorus enrichment was 2.99 t and 3.67 t,respectively.?3?comprehensive evaluation of ecological benefits of Constructed WetlandAccording to the index selection principle,the benefit evaluation index system of the artificial wetland ecosystem is divided into 3 layers:the first layer is the target layer;the second layer is the element layer;the third layer is the index layer;Divided into 20indicators.The evaluation criteria are mainly to select the 10 indicators of water quality in the third layer,bio-first potential productivity,wetland area change rate,vegetation cover rate,annual runoff depth etc.to conduct ecosystem benefits evaluation of constructed wetland.The comprehensive score of ecological benefit of artificial wetland system is0.6795.