title: Occurrence and fate of volatile siloxanes in a municipal wastewater treatment plant of Beijing, China.
abstract: The occurrence and fate of four cyclic and two linear volatile siloxanes were studied in a municipal Wastewater Treatment Plant (WWTP), Beijing City, China. Aqueous and sludge samples were analyzed by solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS). In the studied WWTP, four cyclic analogs (D3-D6) had significantly higher concentrations and frequencies than the two linear analogs [Octamethyltrisiloxane (L3) and Decamethyltetrasiloxane (L4)], with inputs into the WWTP ranging from 78.2 to 387.7 kg/year. Removal efficiencies of volatile cyclic siloxanes in two parallel secondary treatment processes ranged from 59.3 to 92.7%. For volatile cyclic siloxanes, relative fractions of mass loss by adsorption to sludge ranged from 8.3 to 53.0%, and their adsorption capacities were significantly affected by the dissolved organic matter. Besides adsorption, they were eliminated mainly in anaerobic units (44.4-84.3%). Through in vitro biodegradation experiments, we concluded that in the anaerobic compartments, Hexamethylcyclotrisiloxane (D3) and Dodecamethylcyclohexasiloxane (D6) were eliminated mostly by volatilization, while Octamethylcyclotetrasiloxane (D4) and Decamethylcyclopentasiloxane (D5) may be eliminated by both volatilization and degradation. Furthermore, microbe catalysis hydrolysis was identified as one of the main degradation pathways for D4 and D5 in anaerobic compartments.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Shuangqing Road 18#, Haidian District, Beijing 100085, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Xu
authors.forename: Yali
authors.initials: Y
authors.lastname: Shi
authors.forename: Yaqi
authors.initials: Y
authors.lastname: Cai
mesh_terms: D000327:Adsorption; D055598:Chemical Phenomena; D002681:China; D002947:Cities; D006089:Gram-Negative Anaerobic Bacteria / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D006094:Gram-Positive Bacteria / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D006868:Hydrolysis; D009111:Local Government; D012833:Siloxanes / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D062611:Solid Waste / Q000032:analysis*; D012995:Solubility; D014835:Volatilization; D062065:Wastewater / Q000737:chemistry* / Q000382:microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D018508:Water Purification; D014881:Water Supply / Q000032:analysis*
chemical_list: D012833:Siloxanes; D062611:Solid Waste; D062065:Wastewater; D014874:Water Pollutants, Chemical; C114768:decamethylcyclopentasiloxane; C024064:octamethylcyclotetrasiloxane; C024035:hexamethylcyclotrisiloxane; C542115:dodecamethylcyclohexasiloxane