| Constructed wetlands can make full use of rural land resources while purifying tail water and realize the utilization of nitrogen and phosphorus resources.It has the advantages of low investment,low cost,and easy maintenance.Therefore,it is often used as a tail water purification unit for rural domestic sewage.Traditional constructed wetlands have problems such as large area and insufficient reoxygenation capacity.At the same time,the biomass of traditional wetland plants such as vegetables and grasses is small,and the economic added value of canna and zailihua is low.In view of the above problems,this study introduces large biomass forage plants as wetland plants,which has good economic added value while strengthening the utilization of nitrogen and phosphorus in the wetland.And it adopts a non-flooded mode to strengthen the reoxygenation capacity of the system and reduce the floor space.Through the selecting the best operating parameters,continuous monitoring of the water quality of the incoming and outgoing,exploring the effect of non-flooded constructed wetland with forage plants on the purification effect of rural domestic sewage after biological treatment,the research results are as follows:（1）The study on nitrogen and phosphorus absorption kinetics of three forage plants,pennisetum giganteum,sweet pennisetum purpureum and pennisetum hydridum found that pennisetum giganteum is suitable for repairing sewage with high PO43--P concentration and has a wide range of adaptation to NH4+-N,but the absorption effect of NO3--N is general;sweet pennisetum purpureum is suitable for repairing low PO43--P concentration,high NO3--N concentration,but the absorption effect of NH4+-N is general;pennisetum hydridum is suitable for sewage with low NO3--N concentration,but the absorption effect of PO43--P and NH4+-N is not significant.The ceramsite is good for stabilizing p H,river sand is good for phosphorus removal,and zeolite is good for nitrogen removal in the wetland substrates.When the non-flooded wetland is filled with river sand,zeolite,and ceramsite with a volume ratio of 1:3:1from top to bottom,the wetland substrates have the best comprehensive removal effect on nitrogen and phosphorus.（2）In the formal experiment,three groups of wetlands were set up,blank control,pennisetum giganteum planting,and pennisetum hydridum planting respectively.By adjusting the operating parameters of hydraulic load and water inlet method,to explore the best operating parameter.when the hydraulic load is 0.3 m3/（m2·d）,the spray intensity is 5 L/（m2·min）,the spray cycle is 2h,and each cycle is sprayed for 5 minutes and idle for 115 minutes,the non-flooded wetland has best comprehensive treatment effect.According to the single-factor ANOVA test,hydraulic load and water inlet method have significant effects on pollutant removal.（3）During long-term monitoring,the planting of forage plants could significantly enhance the removal of pollutants.The COD removal effect of the three wetlands decreases as the temperature decreases,but there is still a good removal effect throughout the year.The removal effect of NH4+-N is relatively stable.COD and NH4+-N in the effluent could reach the DB32/3462-2020 level A standard.The removal effect of the system for TN and TP showed a trend of decreasing with the decrease of temperature.Both the TN and TP of the effluent of the non-flooded wetland which planted forage plants in the cold and warm seasons both could meet the DB 32/3462-2020 level A standard.（4）Pennisetum giganteum and pennisetum hydridum grew well under suitable climatic and environmental conditions.The yield per mu of pennisetum giganteum and pennisetum hydridum were 34.48 and 22.94 t/mu,respectively.The economic benefits were 15520.0 and2753.1 yuan/mu,respectively.Through the analysis of nitrogen and phosphorus balance,it is found that the contribution rate of wetland nitrogen and phosphorus removal:other effects>plant absorption>plant efficiency. |
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