| With the rapid development of China's economy and urban population,urban sewage emissions was increasing.However,due to environmental infrastructure failed to keep pace with urban development speed,large part of urban sewage was discharged directly without treatment,so urban sewage water was as a result of a major source of pollution.Urban sewage containing massive COD, NH3-N,heavy metals ere pollution composition,these pollutants can easily enter the body through the food chain to caused serious damage of people's health.Therefore urban sewage treatment has become the important environmental problems which needed to be resolved urgently.The traditional methods had the disadvantages of great investment,high costs and complicated process,difficult to promote greatly,and was difficult to carry out the depth of nitrogen and phosphorus removal.Therefore,how to screen out repair technologylow of low cost and good effectiveness has become the great subject needed to be resolved urgently.Just for this,the study adopt the method of comprehensive survey and typical investigation to investigate the pollution of wastewater about the main city sewage treatment plant(including Fuzhou, Xiamen,Quanzhou,Zhangzhou,Putian,Longyan,Nanping)of Fujian province.The study analyzed the situation of the main sewage treatment plants in Fujian Province from the daily capacity,service area, service population,area,SS,TN,NH3-N,TP,COD and heavy metal pollution.On the basis of overall understanding of domestic sewage's pollution features about main city of Fujian province,by the simulated test,utilizing 9 kinds of aquatic plants(Canna indiace,Eichhornia crassipes,Alternanthera philoxeroides,Commelina communis,Cyperus alternifoliu,Polygonum longisetum,Nelumbo nucifera, Zizania latifolia,Cyperus malaccensis var.brevifolius),we carded through the removing study of simulation sewage and heavy metal pollution and the actual removing effect of domestic sewage, discussed removing effect of different aquatic plants.We tried to screen out aquatic plants which are suitable for sewage purification.The main results of study are as follows:1.The result of investigations in 7cities of Fujian province showed that:sewage treatment in different cities was quite different.According to grade two of integrated wastewater discharge standard (GB8978-1996),TP,COD exceeded the standard,7 kinds of heavy metal content was low.According to national ground water environment quality level V standard(GB3838-2002),TN,NH3-N,TP,COD exceeded the standard and only the content of Cu and Zn did not exceed the standard,other four heavy metals all exceeded the standard.The content of Cd in Zhangzhou,Xiamen,Putian,Quanzhou all exceeded the standard 1.0 times;The content of Cr in Xiamen,Quanzhou respectively exceeded the standard 0.2 and 0.6 times;The content of Pb in Zhangzhou,Xiamen,Putian,Quanzhou Longyan, Nanping exceeded the standard 1.8,1.4,2.9,1.7,1.6 and 1.6 times.2.The analysis of the sewage treatment plant in Fuzhou showed,according to grade two of integrated wastewater discharge standard(GB8978-1996),TP exceeded the standard,apart from Xiangban,the content of COD in other sewage treatment plant exceeded the standard,the content of NH3-N in Daxuecheng and Kuai'an exceeded the standard,Seven kinds of heavy metal content is low, did not exceeded the standard.According to national ground water environment quality level V standard(GB3838-2002),TN, NH3-N,TP,COD exceeded the standard and only the content of Cu and Zn did not exceed the standard, other four heavy metals all exceeded the standard.The content of Cd in Mawei and Kuai'an respectively exceeded the standard 2.0 times and 1.0 times.The content of Cr in Jinshan,Daxuecheng, Mawei and Kuai'an respectively exceeded the standard 0.2 times,0.1 times,3.0 times and 2.2 times. The content of Pb in Xiangban,Daxuecheng,Mawei and Kuai'an respectively exceeded the standard 1.0 times,1.2 times,2.4 times and 1.5 times.3.On the basis of comprehensive surver and understanding of aquatic plants in Fujian province,it was determined to use the following nine kinds of plants as tested plants:Canna indiace,Eichhornia crassipes,Alternanthera philoxeroides,Commelina communis,Cyperus alternifoliu,Polygonum longisetum,Nelumbo nucifera,Zizania latifolia,Cyperus malaccensis var.brevifolius.Through nine kinds of aquatic plants on three different concentration of simulated sewage,the test which compared the ability to remove Nitrogen and phosphorus showed that,the tested aquatic plants have a certain effect,but the ability to absorb Nitrogen and phosphorus showed some difference.This study found that: under mild stress,the removal rate of Alternanthera philoxeroides to NH3-N was the greatest(53.79%), the removal rate of Nelumbo nucifera to TN was the greatest(48.75%),the removal rate of Eichhornia crassipes to TP was the greatest(70.10%).Under moderate stress,the removal rate of Eichhornia crassipes to NH3-N was the greatest(61.39%),the removal rate of Zizania latifolia to TN was the greatest(52.23%),and the removal rate of Eichhornia crassipes to TP was the greatest(80.15%).Under severe stress,the removal rate of Zizania latifolia to NH3-N was the greatest(55.70%),the removal rate of Eichhornia crassipes to TN and TP was the greatest(respectively for 40.42%,69.58%).Therefor, Eichhornia crassipes,Alternanthera philoxeroides,Zizania latifolia were suitable for urban sewage pollution treatment.4.Through analyzing the nitrogen content in 9 aquatic plants found:under mild,moderate and severe stress,the aerial/underground part nitrogen content in Nelumbo nucifera was greatest.Under mild stress,the content respectively reached 25.85g·kg-1and 23.90g·kg-1;Under moderate stress,the content respectively reached 26.41g·kg-1and 24.09g·kg-1;Under severe stress,the content respectively reached 25.853g·kg-1and 26.18g·kg-1,so Nelumbo nucifera showed the strong enrichment capacity of nitrogen.Under mild stress,aerial part and underground part of nitrogen ratio in Canna indiace,Eichhornia crassipes,Alternanthera philoxeroides,Commelina communis,Polygonum longisetum,Nelumbo nucifera,Cyperus malaccensis var.brevifolius was greater than 1.Under moderate stress,apart from Cyperus alternifoliu and Zizania latifolia,Aerial part and underground part of nitrogen ratio in other 7 aquatic plants was greater than 1.Under severe stress,apart from Cyperus alternifoliu and Nelumbo nucifera,Aerial part and underground part of nitrogen ratio in other 7 aquatic plants was greater than 1. This showed that the sbsorption of nitrogen of these aquatic plants more transferred and accumulated to aerial part,which was favor of urban sewage treatment in nitrogen pollution.5.Through analyzing the phosphorus content in 9 aquatic plants found:Under mild stress,the highest phosphorus content of aerial part was Canna indiace,followed by Alternanthera philoxeroides, respectively for 5.82 g·kg-1and 4.56 g·kg-1,the highest/lowest phosphorus content of underground part was Cyperus malaccensis var.brevifolius/Eichhornia crassipes;Under moderate stress,the highest phosphorus content of aerial part was Canna indiace,followed by Alternanthera philoxeroides, respectively for 6.31 g·kg-1and 5.17 g·kg-1,the highest/lowest phosphorus content of underground part was Canna indiace/Eichhornia crassipes;Under severe stress,the highest phosphorus content of aerial part was Canna indiace,followed by Cyperus alternifoliu,respectively for 5.86g·kg-1and 2.56g·kg-1, the highest/lowest phosphorus content of underground part was Canna indiace/Eichhornia crassipes. So,Canna indiace showed the strong enrichment capacity of phosphorus,was suitable for urban sewage pollution treatment in phosphorus pollution.6.Through analyzing the removal capacity of 9 aquatic plants to Cu,Pb,Zn,Cr found:the removal of Canna indiac and Cyperus malaccensis var.brevifolius to Cu reached minimum value on day 7,the removal of Polygonum longisetum,Alternanthera philoxeroides and CommeIina communis to Cu reached minimum value on day 10,the removal of Eichhornia crassipes to Cu reached minimum value on day 5,and Polygonum longisetum is the removal of Cu highest,reaching 68.78%.Polygonum longisetum is the removal of Pb highest,reaching 79.67%.Eichhornia crassipes is the removal of Zn highest,reaching 43.40%.Polygonum longisetum is the removal of Cr highest,reaching 57.99%.7.Different aquatic plants on the heavy metal accumulation ability were significant difference. Apart from the BCF of Pb in the aerial part of Canna indiace wss less than 1(0.94),other BCF of Pb in the aerial and the underground part of the aquatic plants were greater than 1,so they showed the strong enrichment capacity of 4 kinds of heavy metal.The cumulating coefficient of Eichhornia crassipes to Pb was the strongest(aerial part:15.38,underground part:40.82).The cumulating coefficient of Eichhornia crassipes to Cu was the strongest(aerial part:69.23,underground part:114.33).The cumulating coefficient of Alternanthera philoxeroides's aerial part(8.84/27.39)and Eichhornia crassipes's underground part(18.96/81.41)to Zn/Cr were the strongest.8.Through comparing the ability to remove Nitrogen and phosphorus of seven kinds of aquatic plants showed that,test within 15 days,the ability of seven kinds of aquatic plant to absorb NH3-N was good,the order of adsorption capacity for NH3-N was as follow:Eichhornia crassipes＞Cyperus malaccensis var.brevifolius＞Canna indiace＞Cyperus alternifoliu＞Alternanthera philoxeroides＞Commelina communis＞Polygonum longisetum;the order of adsorption capacity for TN was as follow:Canna indiace＞Cyperus malaccensis var.brevifolius＞Eichhornia crassipes＞Polygonum longisetum＞Cyperus alternifoliu＞Commelina communis＞Alternanthera philoxeroides;the order of adsorption capacity for TP was as follow:Canna indiace＞Cyperus alternifoliu＞Eichhornia crassipes＞Polygonum longisetum＞Commelina communis＞Cyperus malaccensis var. brevifolius＞Alternanthera philoxeroides.9.Through analyzing the nitrogen and phosphorus content in aquatic plants found:The nitrogen content of Cyperus alternifoliu's aerial part was highest,to be 36.14g·kg-1,Eichhornia crassipes's aerial part was lowest,to be 9.03g·kg-1.The nitrogen content of Cyperus alternifoliu's underground part was highest,to be 21.36g·kg-1,Polygonum longisetum's aerial part was lowest,to be 7.92g·kg-1.Apart from Eichhornia crassipes,Aerial part and underground part of nitrogen ratio in other aquatic plants was greater than 1.The phosphorus content of Cyperus alternifoliu's aerial part was highest,to be 11.35g·kg-1, Eichhornia crassipes's aerial part was lowest,to be 1.82g·kg-1.The phosphorus content of Cyperus alternifoliu's underground part was highest,to be 7.63g·kg-1,Polygonum longisetum's aerial part was lowest,to be 2.76g·kg-1.Apart from Cyperus malaccensis vat.brevifolius,Alternanthera philoxeroides, Eichhornia crassipes,Aerial part and underground part of nitrogen ratio in other aquatic plants was greater than 1.This further proved that these aquatic plants had the better adsorption capacity of nitrogen and phosphorus,and Cyperus alternifoliu was suitable for urban sewage pollution treatment. |
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