Study On Enhanced Constructed Wetland For Restoration Of Eutrophic Water

In recent years,constructed wetland treatment technology is becoming eutrophic water processing core technology.Because constructed wetland technology is an efficient,simple and low processing technology,and has aesthetic value.Compliance with international environmental philosophy of small decentralized sewage treatment system,it facilitates the promotion of small and medium towns.The removal of contaminants in constructed wetland system is influenced and restricted by many factors.For the situation,the test proposes biofortification that activated sludge is inoculated on the filler surface,in order to improve the purification effects of contaminants in constructed wetland.The study of this subject is vertical flow constructed wetland system.Through contrast and analysis using biofortification the removal of pollutants at different hydraulic loading and filler layer depth,as well as the effect of microbial biomass,DO,pH and temperature on the constructed wetland systems.The bio-phase of inoculated sludge and microbial morphology in wetlands system is analyzed.Through comparative analysis the removal rate of COD,TP,NH4+-N and TN in the two systems under different hydraulic loading conditions,to determine the optimum hydraulic loading conditions of the test.Hydraulic loading range from 0.2 m3/(m2·d)to 2.5 m3/(m2·d).The results showed that COD and TN removal rate increased and then decreased with the increase of hydraulic loading,and removal rate of NH4+-N and TP gradually decreased with the increase hydraulic loading.Biofortification has significantly an enhanced role in COD removal,and has a promotion of small amplitude on the removal of TP,but the improvement of NH4+-N and TN removal is weak.Considering the trend of the four indicators in two systems to determine the optimal hydraulic loading condition of the test was about 0.6 m3/(m2 · d).Under optimum hydraulic loading(0.6 m3/(m2 · d))condition,the effect of different fillers depth on COD,TP,NH4+-N and TN removal rate was discussed,the test results show that by increasing the filler layer depth,purifying effect of pollutants in the two systems could be improved.The distribution of microbial biomass along the way at various packing layer depth was studied.The results showed that lipid phosphorus of microorganisms in the two groups of the wetland system was reduced at the vertical direction gradually,microbial biomass was in the upper space of wetlands more than that in the lower layer,and microbial biomass was in biofortification system more than that in the blank system.The relationship between microbial biomass and COD removal rate showed a positive correlation trend basically,there is no significant correlation between nitrogen and phosphorus removal and microbial biomass in wetland.The microbial biomass cannot fully reflect the activity of microorganisms,and the relationship that with the pollutant purification capacity is affected by temperature,microorganisms,plants and other comprehensive factors.The effect of DO,pH,microbial biomass and temperature on pollutant removal rate in the two wetland systems was researched.The results showed that the concentration of DO in the internal system increased and then reduced along the packed bed depth.The concentration of DO in biofortification system is less than that in the control system.The removal of pollutants was mainly in the upper area of the wetland system.The pH along the flow direction gradually showed a downward trend.The pH in biofortification system was less than that in the control system.The optimum pH of pollutant removal ranged about between 7.5 and 7.8.The changing trend between the change of temperature and COD and nitrogen removal in the two wetland systems was consistent.The increase on temperature cannot change phosphorus removal in wetland.The bio-phase in the two wetland systems was analyzed.The results showed that the type and quantity of microorganisms did not show large differences,and bio-enhanced technology promoted microbial biomass.The number of protozoa in the upper was more than that in the lower of the two systems.By inoculating sludge,the method did not cause too much impact on the system’s environment,and there was a certain effect on sewage treatment.The experimental results showed that using the biofortification technique to control eutrophic water could achieve good treatment effect.Compare with other processes,its running cost also has obvious advantage,it is feasible in technology and economy.