Water Pollution And Bioremediation Of Urban River In Nan Jing

The water pollution has been received increasing concerns. The emerging phytoremediation techniques, with their lower cost and environmental friendly nature, have been accepted by enormous researchers. Phytoremediation of water with the application of microorganisms is a new-developed strategy having a promising future.During August 2009 to August 2010, a survey about water environment was made in the main city of Nanjing. The main indicators evaluated in 53 monitering sections of the waters in Nanjing included total nitrogen(TN), total phosphorus(TP) and heavy metal{copper(Cu), zinc(Zn), lead(Pb) and cadmium(Cd)}. The results showed that: eutrophication was serious of the rivers in Nanjing. The content of TN in the waters were beyond the standards limit value of the landscape water quality of the National Surface Water Environmental Quality Standards; the highest content of TN of monitering section was 17 times more than the standard value; Compared with the class V standards limit value of Environment Quality Standards for Surface Water, the rivers and waters, which the content of TP, Cd and Pb were exceeded, accounted for 60%,60%and 80%, in the 12 monitering reach, respectively; the content of Cu and Zn were not exceeded. The results of identify indicators of quality comprehensive evaluation showed that:The pollution of rivers and waters were serious in spring, the water quality of Qinhuai river (Wuding door-Simon water segment, Zhu Bridge-big and medium bridges segment) was the poorest in the 12 detected river sections.Our simulated wetland ecosystem were constructed to investigate four hydrophytes removal effect on total nitrogen, total phosphorus and heavy metal, in the same matrix, at different hydraulic retention time, in waste water.The results were that all of the four spicies grew well in the constructed wetland. The removal rate of the four tested plants to copper, zinc and phosphorus were more or less the same. In the hydraulic retention time of 1 day, the four tested aquatic removal rate of copper reached 99%, of zinc was over 80%, of TP closed to 80%; the purification of TN of Iris pseudacorus Linn.and Cyperus alternifolius L.was to 50%, better than Pontederia cordata L. and Arundo donax L.var.versicolor Kunth. The purification of lead and cadmium were mainly depended on the adsorption of matrix.In our research, denitrifying bacterium strains QW, ZW and LR with faster gas producing and higher nitrogen efficiency was screened from the soils that sampled from the rhizosphere of aquatic plant living in the rivers of the main city in Nanjing. PCR amplification, physiological and biochemical characters, homology analysis of 16S rDNA sequence, and characteristics of biologic and denitrification were focused on about strain QW, ZW and LR in our research. The results were that:The cells of screened strains were mostly Gram-negative, facultative anaerobic and rod-shaped. The taxonomic status of strain QW, ZW and LR were determined as Pseudomonas. In addition, strain QW and ZW showed the resistance to CHL, while strain LR resisted to AMP, CHL, ERY and STR. Three strains can use extensive carbon sources with sodium citrate as the most effective one,and the most effective nitrogen sources was potassium nitrate. The effects of temperature, C/N ratio, pH and initial consentration of nitrate on the growth and denitrification process of strains were also investigated with sodium citrate and nitrate as sole carbon and nitrogen source respectively. The results showed that under anoxic condition with temperature at 20℃to 30℃for strain QW and ZW,35℃for strain LR, stains grew fast and exhibit excellent nitrogen removal ability. The favorite initial pH range was 7.0 to 7.5 for strain QW and ZW,8.0 for stain LR.The optimal C/N ratio Was 1. It was also found that nitrogen removal process was mainly happened in the growth phase of the 12-28 hours for stain QW and ZW,16-58 hours for strain LR. Inoculation was not a major limiting factor for denitrification.The removal rate of TN was achieved over 90% with the concentration of 40 mg L-1 nitrate.Under laboratory scale, a test was made to investigate the impact of bioaugmentation by strain QW, ZW and LR to treat waters polluted by nitrate. The results revealed that umbrella root exudates can promote the growth of the three strain; umbrella was slightly enhanced by three stain.