Study On Phosphorus Flame Retardant In Shaanxi Wastewater Treatment Plant

With the gradual ban of brominated flame retardants?BFRs?,the production and usage amount of phosphorus flame retardants?PFRs?has increased rapidly,and was widely used in chemical industry,electronics industry,construction industry,home improvement materials industry and textile industry.PFRs are present in various media in the environment,due to the character of long-distance transport,persistence and bioaccumulation,the pollution levels and risk of PFRs has received attention.Wastewater treatment plants?WWTPs?are an important gathering place of environmental pollutants and an important source of pollution in natural waters.It is of great significance to study the content level and distribution of PFRs in WWTPs,in order to control and degradation of PFRs,block the excessive discharge of PFRs into natural water bodies.It is necessary to conduct regional PFRs pollution level studies and understand the migration and transformation of PFRs in wastewater treatment systems.This study collected the influent and effluent samples and terminal sludge samples of all10 prefecture-level cities,one county-level city?Hancheng?and Yangling Agricultural High-tech Industry Demonstration Zone in Shaanxi Province.The wastewater sample was pretreated by solid phase extraction?SPE?and detected by chromatography-mass spectrometry?GC-MS?.The sludge samples were prepared by ultrasonic extraction?UE?,SPE and Florisil column purification?FL-PR?and was detected by GC-MS.The concentration,distribution and migration of eight PFRs in sewage and sludge were studied.Anaerobic biological sludge method was used to carry out laboratory simulation study on single substance simulated sewage.Three groups were selected to represent PFRs:TPP?phenyl?,TCEP?chlorinated?and TEHP?secondary hexyl?.The removal effect and mass balance of PFRs in anaerobic biological treatment.7 of the 8 target PFRs selected in this study were detected in the WWTPs,and TCP was not detected in all sewage and sludge samples.The concentration of?₇PFRs in the influent ranged from 845.17 to 3792.41 ng/L,and the concentration of?₇PFRs in the effluent ranged from 556.89 to 1859.22 ng/L.TCEP is the most important PFR monomer in both influent and effluent,accounting for 32.81%of the?₇PFRs in the influent and 47.93%of the?₇PFRs in the effluent.The?₇PFRs average removal rate was 15.95%,and the chlorinated PFRs were not substantially removed.The concentration of?₇PFRs in the terminal sludge samples ranged from 88.13 to 1917.10 ng/g dw?dw,dry weight?,TEHP was the main pollutant accounted for 40.42%of?₇PFRs.The level of PFRs in the sludge of four sewage treatment plants in northern Shaanxi is higher in summer than in winter.Compared with domestic and foreign research,the pollution level of PFRs in regional sewage in Shaanxi Province is respectively low,while the chlorinated PFRs are moderately polluted.The level of sludge pollution is much lower than that of foreign countries,but it is at a high level in China.The laboratory simulation study by anaerobic biological sludge method showed that the anaerobic biological sludge method had poor removal effect on chlorinated PFRs after 24 h treatment,and the total amount was almost not removed.The removal rates of TEHP?with Hexyl B?and TPP?with Phenyl?reached 92.82%and 96.71%,respectively in Liquid phase,and the proportions in the solid phase accounted for 85.1%and 96.0%,respectively,most of them were adsorbed by sludge,TEHP was degraded to some extent,and the total removal rate was 50.33%.By using a single PFRs to simulate sewage,it can be concluded that the low removal rate of chlorinated PFRs in the sewage treatment system has a great relationship with the steric hindrance effect of the chlorine atoms themselves,and the steric hindrance effect of TEHP by similar structural substances has a greater impact on its degradation.