A Preliminary Study On Removal Of Targeted OPFRs In Integrated Vertical Flow Constructed Wetlands

The enormous discharge of industrial,domestic wastewaters are the predominant sources of the severe surface water OPFRs pollution,previous studies related to OPFRs have been mostly focused on its spatial and temporal occurrence,possible sources in various environments and potential exposure risk assessment of fish and human,that urgent to adopt a cost-effective way to mitigate OPFRs wastewater.In this paper,the economic and effective adsorption method was availabled to alleviate OPFRs wastewater,that adsorption capacity,difference,influencing factors and adsorption mechanism of different adsorbents on TCEP and TCPP were investigated.The Langmuir model can better described the sorption isotherm,the maximum adsorption capacity for OPFRs increased in the order of biochar(12.30-17.77mg/g)>> igneous rocks(40.91-67.11?g/g)>zeolite(36.81-62.59?g/ g)>soil(7.08-10.64?g/g),whose different adsorption rate and capacity were greatly related to the adsorbate molecule size and hydrophobicity,also adsorbent particle size,specific surface area,charge,-OH and-COOH groups that leads to the variability of available adsorption sites.The adsorbed amount of TCEP,TCPP increased with a higher pH and lower concentration of soil HA,which is attributed to the electrostatic interaction between the protonated P=O in OPFRs and negative adsorbent,or the formation of hydrogen bonding between P=O and-COOH,-OH,-C=O,-CHO groups in HA.Biomass carbon raw materials and pyrolysis temperature would affect the adsorption behavior of biochar,for the weak hydrophobic OPFRs,selecting abundant contain of lignin,crystaled cellulose raw materials,simultaneously,at the moderate pyrolysis temperature(500-600?)can derive larger specific surface area,quinoid C=O contents which induce stronger hydrogen bonding bridge.Therefore,based on the sorption behavior of TCEP,TCPP in different adsorbents,hydrophobic,electrostatic and hydrogen bonding were proposed to be involved in the sorption process,and their contribution may be more rely on the hydrophilic/hydrophobic properties of the sorbent/sorbate and the quantity of C=O groups in sorbent.Secondly,we conducted to explore the effects of different operation modes(drywet alternation,resting period and continuous operation)in a field pilot IVCWs for treating low C/N synthetic wastewater.The results showed that dry(2d)-wet(5d)alternation cannot overcome the reduction of temperature,resulting in the reduction of nutrient removal,and the TN efficiency sharply decreased by up to 26.45%.Over the experiment period,IVCWs had a preferable performances on NH4+-N(71.5±13.06%),COD(61.21±8.11%),TN(56.35±11.41%)and TP(49.69± 8.5%),and the removal contribution of VF1(54.92-86.83%)over 50% reflected its effective and potential.Interestingly,the massive accumulation of NO3--N in VF2 would weakens removal of TN,and how to induce the processes of Anammox was particularly critical.Finally,we have simulated the discharge and migration behaviour of WWTPs and other sewage targeted OPFRs in IVCWs micro-water environment,to observe the removal efficiency and contribution of each component,the occurrence,fate and discrepancy on water-sediment-plant phase that related mechanism were studied.For TCP,TCEP and TCPP concentrations of 246.14±69.62?g/L,919.59±193.96?g/L and 808.31±200.55?g/L,the removal efficiencies were 70.18±13.98%,51.76±18.07% and 60.28±20.05%,respectively.Plant and sole substrate accumulation accounted for 0.006-0.022% and 23.90-69.92% of the total removal,respectively,indicating that the majority(30.07-76.09%)was removed by photodegradation,microbial degradation and other pathways.Furthermore,the accumulations of selected OPFRs in sediments were successively igneous rock > zeolite > soil,while it's on the over water column of P· australis(0.79±0.15-108.22±10.76ng/g)and C· alternifolius(3.16±0.06-127.44 ng /g)were merely small.The mass balance calculation shows that 12.64-49.22%,29.61-47.11% of inlet OPFRs mass load can be accumulated in sediments and effluent water,which may lead to its persistent existence in sediments or travel to a wider range of water bodies.When compared to the occurrence and migration behaviors of targeted OPFRs,indicating high hydrophobic TCP was easier adsorbed on sediments or roots surface,moderate hydrophobic TCPP was more liable to be translocated acropetally,and low hydrophobicity of TCEP may be absorbed directly by plants.It was worth noted that the removal performance of OPFRs in the long-term operation of CWs,its occurrence,accumulation and persistence in soil,and whose influences on the growth of phytoplankton and macrophytes were eye-catching.