| The consumption of organophosphate flame retardants(OPFRs)in the world is increasing year by year.As an addication,it is incorporated into various materials to enhance the flame resistance.Under the effects of volatilization,leaching and abrasion,OPFRs in the material are easily released into the environment.In recent years,OPFRs have entered water bodies in large quantities through industrial point source pollution,urban non-point source pollution,and atmospheric subsidence.This has caused potential safety hazards to the water environment and human health.Therefore,it is of great practical significance to study the removal technology,migration technology and transformation laws of OPFRs in water bodies.Constructed wetland technology is a simple and effective water treatment technology.In recent years,it has been widely used in pollution control of emerging pollutants(EC)such as organophosphorus pesticides.However,the current research on the removal of OPFRs in water by constructed wetland is very rare.The subjects of this experiment are the two most common OPFRs in the water environment,Tris(2-chloro)propyl phosphate(TCPP)and Tris(2-chloro)ethyl phosphate(TCEP).The removal effect and main influencing factors of TCPP and TCEP in the composite vertical flow constructed wetland were studied,and the microbial community structure in the constructed wetland was analyzed.The purpose of the study is to provide a certain theoretical basis and reference for the treatment technology and ecological restoration of OPFRs polluted water bodies.The experiment obtained the following main conclusions:(1)The constructed wetland device has a good removal effect on TCPP and TCEP.With the introduction of simulated wastewater with TCPP and TCEP concentrations of about 1 mg/L each(the water quality is based on the Sewage treatment plant Class B standard as the reference standard)and the hydraulic residence time HRT is 2.6d,the average removal rates of TCPP and TCEP reached 66.94% and 45.97%.The composite vertical flow wetland downflow cell has higher removal effect on the two OPFRs than the upflow cell,and the removal contribution rate of the third cell along the process is the highest,accounting for 71.3% and 48.18% of the total removal rate,respectively.(2)Compared with the accumulation effects of substrate,plant and mud on TCPP and TCEP,the mechanisms of microbial degradation,transformation,hydrolysis and evaporation in constructed wetland contribute more to the removal of TCPP and TCEP.However,substrates,plants,and mud provide attachment beds for microorganisms,which indirectly promotes the removal of TCPP and TCEP in constructed wetland.(3)Plant planting significantly promoted the removal of OPFRs in constructed wetland.After planting windmill grass(Cyperus alternifolius)in composite vertical flow constructed wetland,the removal rates of TCPP and TCEP increased by 16.21%and 19.42%,respectively.(4)The concentration of exogenous organic matter in wastewater has a significant effect on the removal of OPFRs in constructed wetland.The concentration of exogenous organic matter in simulated wastewater increased from 60mg/L to 80mg/L,and the removal rates of TCPP and TCEP decreased by 12.26% and 3.51%,respectively.The dissolved oxygen concentration in the constructed wetland was positively correlated with the removal rate of TCPP and TCEP.(5)The microbial abundance in the last 1/2 section of the constructed wetland device is higher than that in the first 1/2 section,but the total number of microorganisms at each point decreases after adding simulated wastewater containing TCPP and TCEP.The dominant bacteria in the constructed wetland plant are Proteobacteria,Actinobacteria,Chloroflexi,Acidobacteria,and Bacteroidetes.The microbial community structure of the inner surface substrate and the bottom substrate of the constructed wetland is similar,but the difference between the microbial community in the mud and the substrate is obvious. |
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