Study On The Remediation Of Black-odor Water Body By Aquatic Plants With Plant Growth-promoting Rhizobacteria

With the rapid development of the economy and the continuous improvement of people’s living standards,industrial wastewater and excessive discharge of domestic sewage have caused serious damage to the water ecosystem,resulting in black-odor water bodies,which not only damages the surrounding environment and restricts the construction of ecological civilization in China,but also affect the well-being of residents.Therefore,the remediation and improvement of black odorous water bodies are the focus of current and future environmental protection work and urban construction.To explore an effective,environmental,rapid operating method to repair black and odor water bodies,water samples and sediment samples collected from a polluted municipal lake in Daqing,China,and adopts the remediation method of aquatic plants with plant grouth-promoting bacteria（PGPR）to carry out laboratory simulation and explore the remediation effect and mechanism of the combined process on black odor water bodies.Through nearly 8months of laboratory experiments and pilot test studies,the following conclusions can be drawn.In an experimental study of four different aquatic plants,namely,Elodea canadensis Michx,Vallisneria natans（Lour.）,Hara Elodea nuttallii（Planch.）H.St.John and Ceratophyllum demersum L,for the in-situ removal of typical persistent organic pollutants COD,NH₄⁺-N,NO3-N and TP from black-odor water bodies,it was found that Elodea canadensis Michx had the best removal effect on the above four pollutants with the removal rates of 34.41%,22.95%,45.71%and 43.80%,respectively.In the study compared the remediation performances using one,two,three,and four pieces of Elodea canadensis Michx per 0.05 m²found that when the transplanting density was one piece per 0.05 m²,the best effect on the remediation of black-odor water bodies was achieved,and the removal rates of COD,NH₄⁺-N,NO₃-N and TP were44.01%,29.75%,46.83%,and 49.33%,respectively.In a comparative analysis of the effectiveness of the Elodea canadensis Michx and the effectiveness of the Elodea canadensis Michx with PGPR in the remediation of black-odor water bodies,it was found that the Elodea canadensis Michx with PGPR had a higher removal rate of pollutants,indicating that the remediation system with the PGPR was more effective.In the four dosages of PGPR（0.25 g,0.5 g,0.75 g,1.0 g）on the remediation of repairing black-odor water bodies,it was found that when the dosage of PGPR was 0.5 g,the repair effect of black-odor water bodies was the best,and the removal rates of COD,NH₄⁺-N,NO₃-N and TP were 67.79%,45.65%,58.31%and63.94%,respectively.The study of environmental factors such as DO,p H and temperature on the remediation of black-odor water bodies by Elodea canadensis Michx with PGPR.The optimum remediation results were obtained when the water environment conditions were 20℃<T<22℃,p H=7 and DO=4 mg/L,and one Elodea canadensis Michx per 0.05 m²with 0.5g PGPR.Applying these optimal conditions to a water tank（216 L）in a pilot test,the removal rates for COD,NH₄⁺-N,NO3-N and TP were 89.34%,60.12%,69.74%and 75.67%respectively,with the large size test performing even better than the small size test,and estimated the remediation cost based on this operational parameter.By comparing the microbial community and functional of dominant bacteria in the raw water,the water remediation by Elodea canadensis Michx,and the water remediation by Elodea canadensis Michx with PGPR.It was found that NH₄⁺-N and NO₃-N were ultimately transformed into N₂,PO₄^3-was ultimately transformed into PH₃.NH₄⁺-N,NO₃-N,PO₄^3-,and organic matter that were not converted into gases were either directly absorbed by plants as nutrients or transformed into plant-absorbable nutrients by dominant bacteria before being absorbed by plants;it has been confirmed that the positive effect of PGPR in the remediation of black-odor water bodies.