Degradation And Removal Of Organophosphate Esters In Wastewater Treatment Systems

Organophosphates(OPEs)have potential environmental risks due to their toxic effects and are widely detected in the environment.Sewage treatment plants(STPs)are the most important source of environmental emissions for OPEs,and their fate in STPs significantly affects their environmental risks.This paper studies the removal efficiency of 9 kinds of OPEs in STPs biochemical treatment,physicochemical treatment and advanced oxidation treatment to assess the environmental fate and risk of OPEs,and provide methods for OPEs wastewater treatment.A GC–MS/MS instrument analysis method for OPEs in water was established.An extraction method for OPEs in sludge suspension was established.The biodegradation law of OPEs under different oxygen conditions was studied,and the results showed that the biodegradation rate of OPEs under aerobic conditions was significantly higher than that under anaerobic conditions.The addition of Fe Cl3 and Fe powder can promote the degradation rate of triphenyl ester OPEs,the addition of electron donors and rhamnolipids can promote the removal of chlorinated OPEs.Alkyl OPEs has low anaerobic degradability,any treatment does not promote its removal.The biodegradation of OPEs has a lot to do with the structure of OPEs.The anion indicates that the active agent Tween 80 has a certain degree of anaerobic degradation of all OPEs.When polyacrylamide(PAM)is used as a coagulant aid,different coagulants have the best coagulation removal effect on OPEs.It is found that the optimal use amount of polyaluminum chloride(PAC)is 100 mg·L^-1,and the removal rate of tris(2-chloroethyl)phosphate(TCEP)at the optimal use amount is 51%,and the other 5 kinds of OPEs The removal rate of PAC can reach more than 70%;the best p H for PAC is 7-9,which is not conducive to coagulation of PAC under acidic conditions.The optimal dosage of aluminum chloride hexahydrate(Al Cl3·6H2O)is 50 mg·L^-1.Under these conditions,the removal rate of OPEs can reach more than 80%.The suitable p H of Al Cl3·6H2O is 5-7.When the p H is greater than 7,the removal rate will decrease,and the decrease can reach 30%.O₃ is conducive to the degradation of OPEs in water.Except for some difficult-to-degrade OPEs,the removal rate of triphenyl phosphate(TPh P)and TCEP is lower,below 30%,and the removal rate of most OPEs is above 80%.The use of O₃ plus ultraviolet light(UV)or aluminum oxide(Al2O₃)can significantly promote the decomposition of refractory OPEs(TPh P and TCEP),and the removal rate can reach more than 70%in 3 hours.O₃ plus titanium dioxide(Ti O2)did not significantly promote the removal of OPEs.Ultraviolet light irradiation has a certain effect on the degradation of OPEs.The removal rate of tricresyl phosphate(m-TTP)and tri-ortho-cresyl phosphate(o-TTP)reaches more than 90%at 30 min.Tributyl phosphate(TBP),Triisobutyl phosphate(Ti BP),TPh P and tripropyl phosphate(TPr P)have a slower degradation rate under ultraviolet light,and the removal rate is between 25%and 70%at 3 h,while TCEP and TDCP is less than 10%in 3 h.Nano-Ti O2 catalyzed by ultraviolet light can increase the degradation rate of OPEs.The removal rate of TBP,Ti BP,and TPRP can reach more than 90%in 2 h,and the removal rate of TDCP and TCEP has been significantly improved to 53%and 40.1%.Bismuth molybdate catalyzed visible light basically did not remove OPEs in water,and the removal rate was less than 10%at 3 h.Silver nitrate catalyzed visible light has a stronger treatment effect on OPEs than bismuth molybdate.The 3 h removal rate of TPh P,m-TTP and o-TTP was increased by more than 30%,and the removal rate of the other five OPEs was also increased by about 10%.The visible light catalytic activity of phosphotungstic acid is between bismuth molybdate and silver nitrate,and the removal rate of OPEs in 3 h is 8.3%?35.3%.On the whole,the degradation efficiency of visible light for OPEs is lower than that of ultraviolet light,but visible light is more energy-saving and has good development prospects.