| As a kind of synthetic polymers, most oligomers of Organosiloxane are volatile and are named as volatile methyl siloxane (VMSs). Being the basic raw materials of silicone products, they are widely added in all sorts of consumer goods, especially in household goods and personal care products. Because of their biological estrogenic effects, they have adverse effects on the human immune system and may also cause damage to connective tissue, lung, liver and other organs. Besides, they have been identified by the OECD and the United States Environmental Protection Agency as high production chemicals (HPV) with a large environmental load. Among emissions of the VMSs into the environment, more than 90% are directly into the air and about 10% are into the sewage. Sewage contains large amounts of polydimethylsiloxane first enters into the municipal sewage treatment plants, which plays an important role in controlling and blocking VMSs into the natural water. However, the effects of different treatment processes on their removal have been rarely reported.In this work, five kinds of VMSs (D3, D4, D5, D6 and L5) are chosen for the study and a micro-ultrasound-assisted liquid-liquid extraction method combined with the GC-MS is used for determining the content of VMSs in sewage. With this method, the concentration levels, distribution and source of five kinds of VMSs in 11 municipal sewage treatment plants at Dalian City, Liaoning Province are determined. The removal efficiency of 5 kinds of VMSs in the wastewater treatment plants are described and the effects of different treatment processes on their removal efficiency are explored as well. The results are as following:The recovery rates of the five kinds of VMSs range from 79.21% to 103.2%, the RSDs are between 4.22%～18.82% and the detection limit reaches 5.54-26.4ng/L, which shows better precision and accuracy and in line with trace detection needs.The total average level of the import of cyclic siloxanes (D3-D6) in 11 municipal sewage treatment plants is 1374 ± 805.4ng/L and the total export is 545.1±296.1ng/L. The concentration level of the import of linear silicone L5 is 12.73±4.60 and the export is 5.342±2.03 ng/L. The average concentrations of D3-D6 and L5 in the import samples are 32.40～142.2,144.4～599.3,179.5～1627,83.36～1130,4.270～19.11 ng/L while they are ND～59.65,80.27～389.9,56.90～345.2,60.56～477.9,3.422～8.968 ng/L in the export samples. Compared with the domestic and international coverage, the concentrations of volatile silicone in the sewage treatment plant in Dalian reported in this paper are relatively low. The volatile silicones come from household and personal care products. As to removal efficiency, L5 is the highest(>70%) and D3、D5 and D6 are very high(>60%). However, D4 is low(<60%). Compared with other reports, lower removal efficiency is reported in this paper. Besides, this study shows that the effects of different treatment on VMSs’removal efficiency are insignificant. |
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