| Agricultural non-point source pollution is a major problem in rural environmental protection in China.Livestock and poultry breeding wastewater is one of the main sources of pollution for agricultural non-point source pollution.Ditch interception and decontamination technology are an important means of aquaculture wastewater treatment,However there are some disadvantages,such as high management cost,poor process stability,poor purification effect,low survival rate of plants and plant death in winter.In the construction of social ecological civilization guided by low-carbon loss,It is of great significance to establish an ecological remediation technology for aquaculture wastewater with high efficient purification and low maintenance cost.In this study,suitable woody plants,economic aquatic herbs,ornamental aquatic herbs and fillers with strong ability to remove pollutants were selected to construct a new type of composite ecological ditch.Then,the influence of influent concentration and flow rate on the decontamination effect of the ditch was studied.Finally,an example application was carried out to explore the purification effect of the new composite ecological ditch on the aquaculture wastewater under long-term operation.The new composite ecological ditches constructed in this study provides a new idea for the treatment of livestock and poultry breeding wastewater.The main conclusions are as follows:（1）The seven woody plant treatment groups of Hibiscus tiliaceus,Hibiscus mutabilis,Glochidion puberum,Elaeocarpus hainanensis,Callistemon rigidus,Bischofia javanica and Cep Halanthus occidentalis had certain removal effects on various pollutants in the sewage.Compared with the blank control,the Cep Halanthus occidentalis treatment group had the best removal effect on total nitrogen（TN）and ammonia nitrogen（NH4+-N）in wastewater and the removal rates were 83.83%and 92.86%respectively;followed by the Callistemon rigidus treatment group.The Glochidion puberum treatment group had the best effect on TP removal in sewage,and the removal rate was 95.32%,followed by the Callistemon rigidus treatment group.The best effect on the concentration of dissolved oxygen（DO）in water was the Cep Halanthus occidentalis treatment group.Six kinds of aquatic herb treatment groups of Canna indica,Thalia dealbata,Hygrop Hila salicifolia,Zizania latifolia,Alternanthera p Hiloxeroides and Hymenachne insulicola had certain removal effects on various pollutants.Compared with blank control,the removal efficiency of TN and TP of Thalia dealbata treatment group was the best,and the removal rates were 95.15%and 99.16%respectively.The Canna indica treatment group had the best removal effect on NH4+-N in wastewater,and the removal rate was 98.79%.The best effect on the concentration of dissolved oxygen（DO）in water is the Canna indica treatment group.（2）In order to screen out the filler combination with better water purification effect and economy,the indoor simulated water test of waste brick,gravel,biomass coke,biomass coke+broken brick,broken brick+gravel,biomass coke+gravel was designed.The results showed that six groups of fillers had certain removal effects on TN and TP in wastewater.Different packing combinations had great differences in the removal rate of TN and TP.Among them,the best removal effect on TN was biomass coke+broken brick group,the rate was 45.01%;the best removal effect of TP was broken brick+gravel group,the rate was 13.05%.It can be seen that the removal rate of TN and TP in water by layered graded fillers was higher than that of single particle size filler.（3）In this study,three kinds of ditches,including the combination of plant and filler ecological ditches,plant ecological ditches and simple soil ditches were constructed,and the water purification effects of three kinds of ditches under static and flowing water conditions were tested.The results showed that the removal rate of various pollutants in the water body under the conditions of static and flowing water was the combination of plant and filler ecological ditches>plant ecological ditches>simid soil ditches.The effects of the influent concentration on the water purification effect of the ditch under the conditions of static and flowing water were discussed.The results showed that the TN,TP,COD,NH4+-N and turbidity concentrations of the water and soil in the combination of plant and filler were high,and the turbidity concentration decreases rapidly.The total amount was large,but the removal rate was low.The influence of influent flow on the water purification effect of the ditches was discussed.The results showed that when the influent flow rate was high,the plant and filler combination ecological ditches had higher removal rates of TN,TP,COD and NH4+-N in water;plants and fillers had low influent flow rate.The combination of ecological ditches had a higher removal rate of turbidity in water.In summary,proper increase of influent concentration and influent flow rate could improve the water purification efficiency of ecological ditches combined with plants and fillers.（4）An example application test was carried out in a goose farm in Haifeng County,Shanwei City,and a plant-fillering combination ecological ditch was constructed to remove aquaculture wastewater pollutants.During the one-month continuous operation of the ecological ditches,the average concentrations of TN,TP,NH4+-N,COD and turbidity in the water quality of the inlet were 11.68 mg/L,8.37 mg/L,5.29 mg/L,184.37 mg,and 119.60NTU respectively.The average concentration of TN,TP,NH4+-N,COD and turbidity in the water quality of the outlet were 6.00 mg/L,0.62 mg/L,1.42 mg/L,39.20 mg/L,21.41 NTU,respectively.The average removal rates of TN,TP,NH4+-N,COD and turbidity in sewage were 48.86%,92.78%,72.82%,73.92%and 81.97%.After the end of the experiment,the content of TN in Canna indica was the highest,and the content of TP in Hymenachne insulicola was the most. |
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