| CWs use physical,chemical,and biological synergies to deal with water pollution.Among them,nitrogen removal mainly depends on nitrification-denitrification in the system.Phosphorus removal depends on substrate and plant adsorption and biological methods to remove phosphorus.The addition of rock wool has an impact on the physical,chemical,and biological mechanisms in the system.In order to improve the ability of the artificial wetland to treat nearshore aquaculture water,it can be improved by setting up an optimal combination.In this study,a small-scale test device was constructed for the artificial wetland system after adding rock wool to determine the water quality purification effect and operating mechanism of the rock wool-artificial wetland.Using rock wool under different salinities,different total phosphorus concentrations,and different environmental conditions,the improvement of the removal effect of the rock wool-artificial wetland system under salt stress and low temperature in winter,as well as the plant growth and microbial community changes in the device were studied.The results as follow:(1)Determined the optimal influent conditions and plant configuration in the constructed wetland system(influent salinity is 1,C/N/P is 25/5/2(COD=50 mg/L,TN=10 mg/L,TP= 4 mg/L),HRT = 4 d),and verify it by analysis of the number,type and activity of microorganisms.The removal rates of TN and TP were 90 % and 95 %,respectively,and the removal rate of COD was 60 %.The chlorophyll(SPAD value),SOD and MDA of Canna are 40.6,1212 U/g and 2.45 nmol/g,respectively,and the amino acid content is 1.82 %.The structure of the microbial community in the constructed wetland has also been optimized,and the dominant flora is the Proteobacteria,a functional flora commonly found in wastewater treatment.(2)When rock wool is used as a matrix material,the water treatment effect of the rock wool device is studied,and the electron microscope scan is used to analyze the internal structure of the rock wool before and after the film is hung.Rock wool,due to its own thermal insulation,hydrophobicity,and fiber structure,can provide more favorable conditions for the adhesion of microorganisms during the operation of the device.At the same time,the different raw materials of rock wool have an impact on the water quality treatment effect,which the A3 device(Rock wool is 7 × 6 cm)has the best treatment effect.Selecting a suitable size can improve the treatment effect.(3)Establish a new matrix material-artificial wetland water treatment system,namely rock wool(slag)-artificial wetland system.The simulated sewage operation was verified under different seasons and different HRT conditions with fixed C / N ratio,different salinity concentration and phosphorus concentration,and the purification effect of the water quality was verified,and the mechanism of phosphorus removal by the device was discussed.The research shows that: the water purification effect of the device is improved,and the system 's water purification effect is improved.It may be that rock wool has played a role,among them,the phosphorus removal effect is good.During the operation of the device,the absorption by plants and the substrate by artificial wetlands(rock wool,quartz sand)and biological phosphorus removal.(4)The rockwool-artificial wetland system was analyzed experimentally,and the changes in the removal effects of nitrogen,phosphorus and other pollutants that had significant influence factors were discussed to determine the optimal operating conditions.The best position of rock wool and the best water-intake conditions are the positions in CW-A7(rock wool is placed on the artificial wetland device 25 cm from the bottom and 5cm from the bottom),when the C/N/P is 25/5/2(COD=50 mg/L,TN=10 mg/L,TP= 4 mg/L),the influent salinity of 1,the P removal rate can reach 97.97 %.In this experiment,high-throughput sequencing was used to test the microbial diversity in the device,and the results were verified by analysis of plant roots,quartz sand,and rockwool microorganisms.The composition and structure of the microbial community in the device are uniform and abundant.Among them,Proteobacteria,Cyanobacteria,and Firmicutes are the dominant bacteria groups,and the water treatment effect is improved.In summary,this paper studies the operating mechanism of constructed wetlands,constructs a small-scale test device,reveals the nitrogen removal mechanism and phosphorus migration and transformation in the system,and explores the mechanism of rockwool-artificial wetlands under salt stress and low temperature in winter. |
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