| In recent years,as people’s living standards continue to rise,the pollution level of urban domestic sewage continues to increase.As a simple and low-cost wastewater treatment technology,constructed wetland has its unique advantages of imitation of nature,long-term operation and landscape greening Used in urban sewage treatment.However,the constructed wetland is an natural,long-term exposed wastewater treatment facility which mainly relies on the treatment of plants,microorganisms and substrate to purify the sewage,the removal efficiency and operational efficiency of the constructed pollutants are affected by many factors.Due to climatic and hydrological conditions,the construction and operation of local constructed wetlands are limited iIn Northeast China.In this report,we research different factors and the influence of different wetland components on the performance of typical constructed wetlands in northeastern China.Combined with the engineering of constructed wetlands,optimize treatment efficiency were put forward to provide reference and support for long-term and stable operation of wetlands.In this study,a typical surface-flow constructed wetland in Northeast China was selected as the research object.A six-month outdoor simulation experiment was conducted to study the effects of different factors on the wetland treatment efficiency.The growth status of wetland plants and microorganisms was also examined.Finally,Typical project cases,here are the results:（1）Seasonal factors are the main factors affecting the treatment efficiency of pollutants in constructed wetlands.Outdoor temperature,rainfall,and sunshine duration are the main influencing factors.The average removal rate of COD in three months is 33.92%,43.60%,and 48.18%.The NH3-N removal rate changed to 41.73%,46.13%,and 44.86%.The results show that the pollutant removal efficiency is higher when the air temperature is between 25-30°C,and the removal rate of COD is not affected by temperature.The removal rate of NH3-N is fluctuating by temperature.The amount of rainfall determines the hydraulic load on the wetland,which indirectly affects the pollution load at the inlet and outlet.Sunshine time affects the growth of plants.When the sunshine duration is 7 h/d,the plant growth is relatively strong and the pollutant removal efficiency is high.（2）DO levels in different seasons had different effects on the removal of COD and ammonia nitrogen in the wetland system.In July,the removal rates of DO and wetland COD and NH3-N were significantly and highly significant respectively.In August,DO was a significant correlation between COD removal rates in wetlands and a significant correlation between NH3-N in wetlands.In September,there was a significant correlation between dissolved oxygen and COD and NH3-N removal rates in wetlands,and COD changes in DO and wetland systems.The correlation is lower than that of NH3-N,which is significantly correlated with the removal rate of COD,and extremely highly correlated with the removal rate of NH3-N.The change of pH value in wetland water has a significant impact on the number of nitrifying bacteria and denitrifying bacteria.The internal pH of the wetland is maintained at 6.8-7.1,which is more suitable for the growth of bacteria.（3）The correlation between the hydraulic retention time and wetland COD removal rate was significant,and it was significantly correlated with the removal rate of NH3-N.HRT control had the best removal effect between 48 and 60 hours,and the best hydraulic retention time was 48 hours.At this point,the inflow rate was 9.5L/h,and the hydraulic load was 0.228 m3/（m2·d）.（4）The results of microbiological determination at different depths for 7,8,and9 months showed that the number of microorganisms was:bacteria>fungi>actinomycetes,among which bacteria accounted for the most in wetland microbial groups,with an order of magnitude of 107,followed by fungus,order of magnitude.From 106 to 107,the number of actinomycetes was the lowest,only 104 to 105 on the order of magnitude.The distribution characteristics of various microorganisms at different depths within the wetland were in line with:middle>surface>lower.The distribution pattern of three kinds of bacteria:nitrifying bacteria:middle>surface>lower;denitrifying bacteria:surface>middle>lower;ammoniated bacteria:middle>surface>lower.（5）The greater the number of bacteria,the better the removal of COD and NH3-N.Changes in the number of actinomycetes and fungi contribute little to COD removal.Denitrifying bacteria and aminated bacteria have extremely significant influence on the removal efficiency of NH3-N.Nitrifying bacteria are positively correlated with the removal rate of NH3-N.The removal efficiency of NH3-N in the sewage wetland system increases with the number of denitrifying bacteria and ammoniated bacteria.（6）The number and distribution of different types of bacteria in constructed wetlands have a significant influence on the hydraulic retention time.The number of the three types of microorganisms increases with the extension of hydraulic retention time,the hydraulic retention time reaches 48h,the number of three bacteria At most,the removal efficiency of NH3-N in wetlands was the highest,but with the increase of hydraulic retention time,the number of three bacteria,especially ammonifying bacteria and nitrifying bacteria,showed a downward trend,but the growth of denitrifying bacteria was positively correlated with HRT. |
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