Study On The Breeding Status And Control Of Filamentous Algae In The Tailwater Wetland Of Wastewater Treatment Plant

Constructed wetland,as an advanced treatment facility for the tailwater of the wastewater treatment plant,can beautify the ecological environment while achieving a deep reduction of nitrogen and phosphorus in the tailwater.However,due to the poor hydrodynamic conditions of the constructed wetland and the high concentrations of nitrogen and phosphorus in the tailwater,it is very easy to cause algal blooms,especially filamentous algae,which will cause ecological hazards and secondary pollution.This research explored the relationship between filamentous algae breeding with environmental and biological factors by monitoring and analyzing the water environment and filamentous algae breeding status in the tailwater wetland of Changshu Zhongchuang wastewater treatment plant.Meanwhile,Cu SO₄,Prometryn and cinnamic acid were selected to evaluate the control effects of filamentous algae and environmental impacts.This research provided a basis for the control of filamentous algae in the tailwater wetland.The main conclusions were as follows:（1）The filamentous algae in the tailwater wetland of Changshu Zhongchuang wastewater treatment plant were dominated by Spirogyra,and the filamentous algae biomass was slightly different due to the temporal and spatial differences.Among them,the biomass in summer and autumn was the highest,and the biomass of CS8reached 744.57 g/m³ in autumn.Compared with the reed planting area,the cattail planting area was prone to filamentous algae breeding.In addition,the monitoring sites with more filamentous algae had higher NH₄⁺-N、COD_Mn and Chl.a,which indicated that the emersions of filamentous algae.（2）The correlation analysis showed that the coverage of filamentous algae was significantly positively correlated with p H,COD_Mn,Chl.a and seasonal changes,while was significantly negatively correlated with plankton biodiversity and zooplankton density.The biomass of filamentous algae was significantly positively correlated with p H,turbidity,COD_Mn,Chl.a,BOD₅ and phytoplankton density,while was significantly negatively correlated with NO₃^--N and phytoplankton diversity.The increase of p H and the concentration of organic pollutants provided nutrients and a suitable growth environment for the growth of filamentous algae.At the same time,the breeding of filamentous algae would affect the photosynthesis of phytoplankton and the feeding of zooplankton,thereby reducing the biomass and diversity of plankton.（3）Through algae control experiments,it was found that Cu SO₄,Prometryn,and cinnamic acid had the best inhibitory effects on Spirogyra when the concentrations were 8.0 mg/L,2.0 mg/L and 4.0 mg/L,and the inhibition rates were 71.43%,86.43%and 75.07%,respectively.The effects of different agents on various indexes of Spirogyra were different.With the increase of the concentrations of Cu SO₄ and cinnamic acid,the content of Chl.a also decreased,indicating that the photosynthesis of cotton was inhibited.However,with the increase of the concentration of Prometryn,the content of protein was significantly affected,indicating that Prometryn can denature and inactivate the protein.Membrane lipid peroxidation occurred in Spirogyra under the action of the three agents.Spirogyra under the action of Cu SO₄mainly uses SOD and CAT to remove excess free radicals,while cinnamic acid uses SOD and POD to achieve the antioxidant process.However,under the action of Prometryn,the enzyme activities in Spirogyra all decreased except POD.（4）Cu SO₄ and Prometryn had a bad impact on the water environment.The concentrations of TN,TP,and COD_Mn in the water all increased significantly after the addition of the agentia,and the highest reached 10.38 mg/L,0.96 mg/L and 55.75mg/L,respectively.In contrast,cinnamic acid had little impact on the water environment.The low concentration of cinnamic acid was beneficial to the removal of TN,TP and COD_Mn.Judging from the acute toxicity of the luminescent bacteria,the order of toxicity was Prometryn>Cu SO₄>cinnamic acid.In summary,this research took the tailwater wetland of Changshu Zhongchuang wastewater treatment plant as the research object,and analyzed the impact of filamentous algae on water quality and organisms.It was found that the increase of p H,COD_Mn and Chl.a or the decrease of plankton biodiversity could be used to warn the growth of filamentous algae.Cu SO₄,Prometryn and cinnamic acid could inhibit the growth of Spirogyra filamentous algae,but the mechanisms were different.Combining the environmental impact,acute toxicity of water quality and economic analysis in the process of algae control,cinnamic acid was selected as a better agent for the control of filamentous algae in tailwater wetland.When its concentration was1.0 mg/L,it not only had a good inhibitory effect on the growth of Spirogyra filamentous algae,but also had less environmental risk and ecological toxicity.