污水处理厂进出水中环状挥发性甲基硅氧烷(cVMS)浓度季节性变化

Seasonal variation of cVMS concentrations in the influents and effluents of wastewater treatment plants

环状挥发性甲基硅氧烷(cVMS)具有高挥发性和高亲脂性,被确认为潜在全球性污染物.本文采用液-液微萃取法,对大连市内8座污水处理厂进出水中3种环状挥发性甲基硅氧烷(D4、D5、D6)浓度水平进行为期一年监测,探究了进出水中cVMS浓度季节性变化规律.污水厂进出水中cVMS年平均浓度分别为830.2 ng·L^-1和234.8 ng·L^-1,进水cVMS中D4、D5、D6年平均浓度分别为471.9、1.565×10^3、453.6 ng·L^-1,出水cVMS中D4、D5、D6年平均浓度分别为249.3、244.1、210.9 ng·L^-1,cVMS去除率范围为47.2%-84.4%.进水中D4、D5、D6浓度均高于出水,其中D5占比为62.2%.污水厂中进出水中cVMS浓度水平有明显的季节变化规律,冬季较高,春秋较低,冬季进水中cVMS年均浓度是春季的1.57倍,是秋季的2.26倍,冬季出水是春季的1.95倍,是秋季的4.24倍.相比曝气生物滤池(BAF)和循环式活性污泥法(CAST)两种处理工艺,恒水位序批式反应器(CWSBR)工艺对cVMS具有较高的去除率.

Cyclic volatile methylsiloxanes(cVMS) have high volatility and high lipophilicity and they are identified as potential global pollutants that are widely distributed in the environment. In this paper, the concentrations of three cyclic volatile methylsiloxanes(D4, D5, D6) were investigated using liquid-liquid microextraction method in the influents and effluents of eight wastewater treatment plants(WWTPs) in Dalian, China. For a period of one year, the seasonal variation of cVMS concentrations in the influents and effluents was investigated. The annual average concentrations of total siloxanes in the influents and effluents were 830.2 ng·L^-1 and 234.8 ng·L^-1 in WWTPs, respectively. The average concentrations of D4, D5, and D6 in the influents were 471.9 ng·L^-1, 1.565×10^3 ng·L^-1 and 453.6 ng·L^-1, respectively. The average concentrations of D4, D5, and D6 in the effluents were 249.3 ng·L^-1, 244.1 ng·L^-1, and 210.9 ng·L^-1, respectively. In general, the range of cVMS removal efficiency was 47.2%-84.4%. Concentrations of D4、D5、D6 in the influents were higher than those found in the effluents. The percentage ratio of D5 is 62.2%. The concentration of cVMS in the influents and effluents of WWTPs showed obvious seasonal variations, with higher concentration in the winter and lower in the spring and autumn. The average concentration of cVMS in the influents in the winter was 1.57 times that of spring, and 2.26 times that of autumn. And the average concentration in the effluents in the winter was 1.95 times that of spring and 4.24 times that of autumn. Compared to biological aerated filter(BAF) and cyclic activated sludge technology(CAST) processes, constant water level sequencing batch reactor(CWSBR) had higher removal rate for cVMS.