硫酸铝混凝法处理页岩气钻井废水实验

Treatment of Polymer Mud Shale Gas Drilling Wastewater by Coagulation with Al2(SO4)3-PAM

通过探究混凝法处理页岩气钻井废水处理效果,可为水净化处理实际应用提供科技支撑。以川西地区某平台聚合物泥浆页岩气钻井废水为研究对象,比选了4种不同混凝剂,确定投加混凝剂硫酸铝[Al2(SO4)3]和助凝剂聚丙烯酰胺(PAM)对钻井液废水进行处理,采用单因素和正交实验筛选出最佳工艺条件,通过计算化学需氧量(CODCr)的去除率、色度变化、紫外-可见吸收光谱、三维荧光光谱,研究了Al2(SO4)3和PAM复合混凝钻井液废水的特性与污染物去除原理。结果表明,硫酸铝混凝法处理页岩气钻井废水的最佳混凝条件为Al2(SO4)3投加量1.0 g/L,PAM投加量50 mg/L,pH值8左右,搅拌时间为3 min,此时钻井液废水CODCr、色度和UV254去除率分别可达到为81.92%、99.40%和81.02%。紫外-可见光谱显示,混凝能明显降低钻井废水的有机物浓度;三维荧光光谱表明,混凝能去除钻井废水中结构较为稳定的羧甲基纤维素(CMC),极大程度地降低钻井废水中有机污染物的量。处理后废水中的各项污染指标均有较大降幅,且经混凝处理后钻井液废水的分子结构趋于简单,为后续的进一步处理减轻了负荷。需要进一步探究去除过程中烃类物质的荧光吸收峰在一段时间内增强的原因,以及混凝法与其他净水方法协同处理废水技术。

As the natural gas industry has developed in China,drilling wastewater has become a hot topic in industrial wastewater treatment.In this investigation,the removal efficiency of coagulation for treating shale gas drilling wastewater from western Sichuan was studied,aiming to provide technical support for practical applications.Four different flocculants[ferric chloride(FeCl3),pre-hydrolyzed ferric sulfate(PFS),polyaluminium chloride(PAC)and aluminum sulfate Al2(SO4)3]were compared.Al2(SO4)3,augmented with the coagulant aid,polyacrylamide(PAM),was found to be the optimal flocculant for advanced treatment of drilling wastewater.Optimum coagulation conditions were determined by single factor and orthogonal experiments.The physicochemical characteristics of the treated drilling wastewater were analyzed and compared with untreated wastewater using measurements that included chemical oxygen demand(CODCr),cyanide(CN-),UV-Vis absorption and the three-dimensional fluorescence spectrum.The pollutant removal mechanism by Al2(SO4)3 coagulation was also investigated.The optimized coagulation conditions were as follows:Al2(SO4)3 dosage,1.0 g/L;PAM dosage,50 mg/L;pH,8;stirring time,3 min.Under the above conditions,the removal rates of CODCr,CN and UV254 of the drilling fluid wastewater reached 81.92%,99.4%,and 81.02%,respectively.Analysis of the three-dimensional fluorescence and UV-visible spectra indicated that coagulation treatment significantly decreased the concentration of macromolecular organic matter in drilling wastewater.Carboxymethyl cellulose(CMC)in the drilling wastewater was quickly removed and contributed to a significant decrease in the organic content of drilling wastewater.All pollution parameters in the drilling wastewater decreased after treatment with the[Al2(SO4)3]-PAM composite coagulant.Colloids in the wastewater were destabilized,simplifying the solution chemistry and aiding with further treatment of the wastewater.Future research should focus on why the fluorescence absorption peak of hydrocarbons increases during degradation of organic matter and on development of synergistic technologies for wastewater treatment and water purification.