Sun Yu, Huang Liang, Lai Changmiao, Li Huiqiang, Yang Ping
Department of Environmental Science and Engineering, College of Architecture and Environment, Sichuan University, Chengdu, People's Republic of China.
Environ Technol. 2021 Oct;42(24):3736-3746. doi: 10.1080/09593330.2020.1739750. Epub 2020 Mar 20.
Shale gas fracturing flowback fluid contains various degradation difficulty organic compounds after hydraulic fracturing. A hybrid treatment method was developed for treating flowback and produced water (FPW) using pre-treatment (NaClO) followed by the expanded granular sludge bed (EGSB) and moving bed biofilm reactor (MBBR). Gas chromatography-mass spectrometry (GC-MS) was employed to detect organic composition in the FPW, the pre-treated FPW, EGSB and MBBR effluent. FPW had high chemical oxygen demand (COD) (3278 mg/L) and the majority of organic compounds in the FPW composed of alkanes and heteroatomic compounds with polymers and polarity. 20% COD removal was achieved after adding 5 g/L of NaClO in FPW (pH = 7, stirring for 20 mins) as pre-treatment and > C alkanes in FPW were decomposed a lot in the pre-treatment process. The pre-treated FPW was diluted (volumetric ratio of 20%/50%) with synthetic wastewater/pure water. In the final stage of operation, Cl and COD concentration of influent to EGSB-MBBR system was around 7000 ± 100 mg/L and 3000 mg/L. EGSB-MBBR system achieved 93.84% COD removal rate, in which EGSB dominated COD removal (>80%). According to the GC-MS results, EGSB had an increase of C-C compounds and a decrease of less C-C content due to the consumption of > C compounds and low molecular weight (LWM) compounds. Meanwhile, aerobic microorganisms in MBBR metabolized LWM organics which contributed a lot to the COD removal (25.06∼68. 22%). The results indicated that the pre-treatment and biological EGSB-MBBR system could be an efficient option used for FPW treating.
页岩气压裂返排液在水力压裂后含有各种难以降解的有机化合物。开发了一种混合处理方法，用于处理返排液和采出水（FPW），先进行预处理（NaClO），然后采用膨胀颗粒污泥床（EGSB）和移动床生物膜反应器（MBBR）。采用气相色谱 - 质谱联用仪（GC - MS）检测FPW、预处理后的FPW、EGSB和MBBR流出物中的有机成分。FPW的化学需氧量（COD）较高（3278 mg/L），FPW中的大多数有机化合物由烷烃和含聚合物及极性的杂原子化合物组成。在FPW（pH = 7，搅拌20分钟）中添加5 g/L的NaClO作为预处理后，COD去除率达到20%，并且FPW中的>C烷烃在预处理过程中大量分解。预处理后的FPW用合成废水/纯水稀释（体积比为20%/50%）。在运行的最后阶段，EGSB - MBBR系统进水的Cl和COD浓度分别约为7000±100 mg/L和3000 mg/L。EGSB - MBBR系统的COD去除率达到93.84%，其中EGSB对COD去除起主导作用（>80%）。根据GC - MS结果，由于>C化合物和低分子量（LWM）化合物的消耗，EGSB中C - C化合物增加，C - C含量较少的化合物减少。同时，MBBR中的好氧微生物代谢LWM有机物，这对COD去除贡献很大（25.06∼68.22%）。结果表明，预处理和生物EGSB - MBBR系统可能是处理FPW的有效选择。
