Study On Determination And Transfer Behaviors Of Polycyclic Musks In Wastewater Treatment

Polycyclic musk compounds (PCMs) are used frequently as fragrances in washing powders, shampoos and other consumer products, which are supposed to smell nicely. They are hydrophobic and lipophilic, and show weak estrogenic activity. Their large-scale usage, persistence and bioaccumulative potential are of concern. Most studies on environmental pollution from polycyclic musks have been focused on such areas as distribution characteristics, ecotoxicological feasibility and risk evaluation. In China the studies on PCMs was draggle mainly due to the skill of their measurement, still being at the starting stage in many respects. Up to date, the study on PCMs distribution characters and transfer mechanism in environment is one of the difficulties and hotspots in respects of environmental science research.In this study, Galaxolide (HHCB) and Tonalide (AHTN) were chosen as the representative samples of PCMs for study on determination and transfer behaviors in wastewater treatment plant. The pre-treatment and determination procedure were developed for PCMs emerged both in water and sludge. In the procedure, the existence, distribution, transfer and transformation of PCMs in sewage treatment plant (STP) were investigated. It can provide scientific basis for the study on PCMs pollution controlling and the foundation of relevant environmental assessment.In the first, High Performance Liquid Chromatography (HPLC) method and gas chromatography-mass spectrometry (GC/MS) method were compared for determination of PCMs. In HPLC method, longer retention time, much more impurity peak and a baseline drift occurred, showing inapprociate to determination of PCMs. Oasis HLB solid-phase extraction (SPE) as the pre-treatment and selective ion monitoring (SIM) mode in GC/MS were used to determine two representative polycyclic musks HHCB and AHTN in wastewater. A varioty of factors were investigated and a set of conditions were found to be optimal for SPE:hexane as the eluting solvent, 10mL eluting solvent volume,0.5% methanol as organic modifier,0.5-2mL·min-1 eluting rate, and 5-10mL·min-1 flow rate of water sample. This method has good linear relativity, its relative standard deviation ranges from 1.67 to 5.48%, and the detection limits were 0.005μg·L-1 for both of musks.Secondly, a rapid, economic and new analytical method for PCMs from solid matrix-microwave assisted extraction (MAE) coupled with GC/MS was developed successfully. The optimized conditions were as follows:1:1 ratio of dichloromethane and acetone is chosen as extraction solvent and its volume was 15mL, extraction temperature and time set to be 120℃and 25min respectively. Under the conditions, the recoveries of HHCB and AHTN reached 89.65% and 94.43% respectively, and the relative standard deviation was 5.49% for HHCB,7.92% for AHTN. The comparison experiments between the microwave assisted extraction and the ultrasound extraction were carried out, showing that the microwave assisted extraction possesses short duration, simple operation and better accuracy though the two had the similar extraction efficiency.Finally, in the method developed in this study, distribution of polycyclic musks at different units of a municipal wastewater treatment plant was investigated and the transfer of the musks along the wastewater treatment course was discussed. The average concentrations of HHCB and AHTN at the influent of the plant were 1.269 and 0.107μg·L-1,while at the effluent 0.578 and 0.056μg·L-1 respectively. The removal efficiencies were 54.5% and 47.7% respectively. Contents of HHCB and AHTN in the sludge were determinated to be 2.909-10.965 mg·kg-1(dry) and 0.573-2.459mg·kg-1(dry) respectively, being relatively high. Two musks were also determinated in particles emerged in wastewater, and large part of the musks in wastewater were found to be absorbed by particles, implying the most important channel for the musks removed from wastewater. In addition, the HHCB/AHTN ratios in both of wastewater and sludge samples keep the similar range, showing that the two musks had high similarity of removal from sewage at each reactor.