Zhang Heng, Xiong Zhaokun, Ji Fangzhou, Lai Bo, Yang Ping
Department of Environmental Science and Engineering, School of Architecture and Environment, Sichuan University, Chengdu 610065, China.
Department of Environmental Science and Engineering, School of Architecture and Environment, Sichuan University, Chengdu 610065, China.
Chemosphere. 2017 Jun;176:192-201. doi: 10.1016/j.chemosphere.2017.02.122. Epub 2017 Feb 27.
Shale gas drilling flowback fluid (SGDF) generated during shale gas extraction is of great concern due to its high total dissolved solid, radioactive elements and organic matter. To remove the toxic and refractory pollutants in SGDF and improve its biodegradability, a microsacle Fe/Persulfate/O process (mFe/PS/O) was developed to pretreat this wastewater obtained from a shale gas well in southwestern China. First, effects of mFe dosage, O flow rate, PS dosage, pH values on the treatment efficiency of mFe/PS/O process were investigated through single-factor experiments. Afterward, the optimal conditions (i.e., pH = 6.7, mFe dosage = 6.74 g/L, PS = 16.89 mmol/L, O flow rate = 0.73 L/min) were obtained by using response surface methodology (RSM). Under the optimal conditions, high COD removal (75.3%) and BOD/COD ratio (0.49) were obtained after 120 min treatment. Moreover, compared with control experiments (i.e., mFe, O, PS, mFe/O, mFe/PS, O/PS), mFe/PS/O system exerted better performance for pollutants removal in SGDF due to strong synergistic effect between mFe, PS and O. In addition, the decomposition or transformation of the organic pollutants in SGDF was analyzed by using GC-MS. Finally, the reaction mechanism of the mFe/PS/O process was proposed according to the analysis results of SEM-EDS and XRD. It can be concluded that high-efficient mFe/PS/O process was mainly resulted from the combination effect of direct oxidation by ozone and persulfate, heterogeneous and homogeneous catalytic oxidation, Fenton-like reaction and adsorption. Therefore, mFe/PS/O process was proven to be an effective method for pretreatment of SGDF prior to biological treatment.
页岩气开采过程中产生的页岩气钻井返排液（SGDF）因其高总溶解固体、放射性元素和有机物而备受关注。为去除SGDF中的有毒难降解污染物并提高其生物降解性，开发了一种微尺度铁/过硫酸盐/臭氧工艺（mFe/PS/O）来预处理从中国西南部一口页岩气井获得的这种废水。首先，通过单因素实验研究了mFe投加量、臭氧流速、过硫酸盐投加量、pH值对mFe/PS/O工艺处理效果的影响。随后，采用响应面法（RSM）获得了最佳条件（即pH = 6.7，mFe投加量 = 6.74 g/L，过硫酸盐 = 16.89 mmol/L，臭氧流速 = 0.73 L/min）。在最佳条件下，处理120分钟后获得了较高的化学需氧量去除率（75.3%）和生化需氧量与化学需氧量之比（0.49）。此外，与对照实验（即mFe、臭氧、过硫酸盐、mFe/臭氧、mFe/过硫酸盐、臭氧/过硫酸盐）相比，mFe/PS/O系统由于mFe、过硫酸盐和臭氧之间的强协同作用，在去除SGDF中的污染物方面表现出更好的性能。此外，利用气相色谱 - 质谱联用仪（GC - MS）分析了SGDF中有机污染物的分解或转化情况。最后，根据扫描电子显微镜 - 能谱仪（SEM - EDS）和X射线衍射仪（XRD）的分析结果提出了mFe/PS/O工艺的反应机理。可以得出结论，高效的mFe/PS/O工艺主要源于臭氧和过硫酸盐的直接氧化、非均相和均相催化氧化、类芬顿反应以及吸附的联合作用。因此，mFe/PS/O工艺被证明是生物处理前预处理SGDF的有效方法。
