Study On Removal Efficiency And Prediction Model Of Trace Phthalate Esters In Water By Nanofiltration Membrane

Phthalates?PAEs?are one of the typical endocrine disruptors.At present,PAEs are detected more and more frequently in water.If drinking water containing trace amounts of PAEs for a long time,it will not only endanger the human reproductive system,liver and nervous system,but also may even have a "triple effect".How to remove trace amounts of PAEs effectively in water and reduce human health risks has become the current research hotspot.Nanofiltration?NF?membrane with low operating pressure,good trapping effect on organic matter,especially on endocrine disruptors,and no secondary pollution,is considered a green,environmentally friendly and new water treatment technology,which has wide prospect in drinking water treatment.In this study,dimethyl phthalate?DMP?,diethyl phthalate?DEP?,dibutyl phthalate?DBP?and bis?2-ethylhexyl?phthalate?DEHP?were the target substances,and a reliable analytical method was established for the determination of trace PAEs in water.The pollution status of PAEs in L and X waters of the main water sources in the GZ area was investigated systematically,and based on the concentrations of PAEs,the efficiency and mechanism of removing PAEs by NF were studied.At the same time,in order to prevent membrane pollution and improve the separation performance of NF membrane,the removal characteristics of PAEs by combination of ozone,activated carbon and ozone+activated carbon were studied.The combination processes of three pretreatment techniques were compared,and the reliability of the optimal combination process was discussed.In addition,a prediction model for removal of PAEs by NF membrane is also established to provide a reliable theoretical basis for dealing with the risk of excessive PAEs pollution in water source and a better guide for water plant transformation and expansion.The main findings are as follows:?1?PAEs analysis and detection method in water was established The PAEs in water samples were analyzed by SPE-GC-MS.The conditions of SPE were as follows:the pH value of water sample was 2.0,the eluent was dichloromethane+ethyl acetate,and the volume ratio of them was 1:1,the total volume of eluent was 4 mL.The established SPE-GC-MS method not only has good peak shape but also has high resolution when detecting PAEs.In addition,the average recoveries of this method are 86.11%¹05.85%with standard deviations of 1.77%⁴.42%.Trace amounts of PAEs in water Can be successfully determined.?2?The level and status of PAEs pollution in major water sources in GZ area were preliminary understanded through the detection Based on the established SPE-GC-MS method,the PAEs in L and X waters of the main water sources in GZ area were tested.Among the four sampling points,the detection rate of PAEs was 100%.The contents of DMP,DEP,DBP and DEHP were 2.51¹5.59?g/L,1.23³.82?g/L,1.61⁷.65?g/L,and 6.07¹1.91?g/L.The order of total concentration of PAEs was H plant>X water source>S water plant>B water plant,and the distribution of time was as dry period>plain period>abundant period;DMP,DBP and DEHP were the main pollutants in water source L,while DMP and DEHP were the main pollutants in water source X.?3?Efficiency of removal of PAEs by NF membrane was discussed The membrane flux increased with the increase of operational pressure,and decreased with the increase of the initial PAE concentration or Na⁺concentration;The retention rate of PAEs did not change with the increase of operating pressure,but increased with the increase of the initial concentration of PAE or Na⁺concentration;When pH was 7,NF flux was the largest,and PAEs retention rate was more than 80%.When the PAE initial concentration was10?g/L,operating pressure was 0.3MPa,pH=7,and Na⁺concentration was 0.005mol/L,PAEs retention ranged from 72%to 88%,and NF membrane flux was 2.742×10^-3L/m²·s,so the water quality was good,and water production rate was high.?4?Effects of pretreatment technology on removal of PAEs by NF membrane were cleared Activated carbon pretreatment technology:under the condition of influent concentration of PAEs 10?g/L,empty bed contact time of activated carbon 15 min,pH value of water sample 7 and operating pressure of NF 0.2 MPa,the removal rates of DEP,DBP and DEHP ranged from 92%to 99%.The removal effect was good.Ozone pretreatment technology:In the influent PAEs concentration of 10?g/L,ozone dosage of 6.0mg/L,ozone contact time of 15 min,NF operating pressure of 0.3MPa conditions,the removal rates of PAEs were between 80%and 98%,and the removal effect was also good.Ozone+activated carbon pretreatment technology:In the influent PAEs concentration of10?g/L,ozone dosage of 4.0mg/L,ozone contact time of 10 min,activated carbon empty bed contact time of 10 min,and NF operating pressure of 0.2MPa conditions,the removal efficiencises of PAEs were 96%⁹9%,and the treatment effect was very good.From the view of average removal rate,the combination of ozone+NF membrane technology was less than 90%,while the activated carbon+NF membrane and ozone+activated carbon+NF membrane were greater than 95%.On the perspective of environmental protection,energy saving and high efficiency,activated carbon pretreatment should be selected as the protective barrier of NF membrane.The start-up period of hanging film was about 30 days.The biological activated carbon+NF membrane combination process has a good removal effect on the water source with a PAE concentration ranging from 10 to 50?g/L.During the continuous operation of 5 months,the removal rate of PAEs increased steadily and finally stabilized at 90%⁹9%.The biological activated carbon+NF membrane combination process could be used as a deep treatment process for water sources polluted by trace amounts of PAEs.?5?SKK model of NF for the prediction of removing PAEs was established,which can be used to predict the removal rate of PAEs well The predicted value and measured value of SKK removal rate model of nanofiltration membrane were the highest,and the relative error was less than 3%.The MWC-SHP removal rate model are smaller,and the relative error does not exceed 10%;the relative error of CFSD removal rate model is greater than 30%at low concentration of PAEs,while under 10%at high concentration of PAEs.SKK model of nanofiltration membrane can predict the removal rate of PAEs very well.In summary,the main source water in the GZ area has been polluted to some extent by PAEs.The NF membrane technology can effectively remove trace amounts of PAEs in the source water.As an environmentally friendly,energy-saving and efficient pretreatment technology,activated carbon can be significantly increased the removal rate of PAEs for NF membrane;the biofilm formed on the surface of the activated carbon during the continuous operation of the activated carbon+nanofiltration membrane combination process,so that the removal efficiency of PAEs was more excellent and stable;The removal rate of PAEs can be well predicted by the SKK model of NF membrane,which provides a theoretical basis for better evaluating the performance and separation effect of the NF membrane and a reference direction for the operation and management of the NF membrane.