Study On Treatment Of Fracturing Wastewater By Combined Process Of Pretreatment And Biological Method

A lot of wastewater will produced during oil and gas field development process, itmainly comes from the oil drilling, downhole operation, operation and so on. Amongthem, fracturing work mainly used to increase production and augmented injection, butit will return discharge of wastewater during process. The wastewater has thecharacteristics of high content of organic matter and suspended solids content, highstability and refractory etc. If it is not treated, it will bring the bad influence on thesurrounding environment. Therefore, it is vital to find a suitable treatment process.For the composition and characteristics of fracturing wastewater, combined withwastewater treatment after the end-result problems, in order to achieve the standard ofwastewater discharge, we will design the process related to reduce the content oforganic pollutants in wastewater. Based on chemical oxidation and coagulationsedimentation methods, we used two kinds of methods to process fracturingwastewater respectively, and employed orthogonal experiments and single factorexperiments to determine the best reaction conditions; Under the condition, wecombined with two methods, than optimized reaction order; According to oxidation,coagulation, hydrolysis acidification and SBR/SBBR, activated carbon adsorptionprinciple, in order to reduce COD in wastewater as the main target, we proposed acombined processes-“Fenton oxidation-coagulation sedimentation-hydrolysis acidification-SBBR-activated carbon adsorption”, and optimized the experimental conditions ofeach process.Firstly, we analysis the water quality of changing oilfield fracturing wastewater and find the main pollutant (COD:5066mg/L, SS:457mg/L). Second, we s tudy with chemical oxidation and coagulation sedimentation method respectively,through the experiment to determine the best reaction conditions (1) optimal oxidant for Fenton system, the optimum reaction conditions is pH value of3, FeSO4amount of30mg/L, H2O2amount of0.2%;(2) Using coagulation sedimentation to fracturing wastewater, the optimum reaction conditions is PAC amountof80mg/L, PAM amount of4mg/L, clarifying time of0.5h. Combined with two methods, the reaction is Fenton oxidation to coagulation sedimentation. Finally, we used the optimum process conditions-“Fenton oxidation-coagulation sedimentation-hydrolysis acidification-SBBR-activated carbon adsorption”, the optimum reaction conditions (1) hydrolysis acidification: pH value of7.0, the temperature around15℃, HRT for12h,concentration of water pollutants for around1760mg/L;(2) SBBR: instantaneous water, aeration time of8h, precipitation time of0.5h, drainage time of10min, no idle time, sludge concentration of5000mg/L, sludge load of0.150(kgCOD/(kgMLSS.d), and the air is15ml/min;(3) Activated carbon adsorption: pH value of3.0, activated carbon additive quantity is100mg/L, the adsorption time of90min, adjust the water pH value of9.0. Usingthe water quality indexes, the fracturing water can achieve the level of emissions standards.The main innovation points of the paper is the first time to use “Fentonoxidation-coagulation sedimentation-hydrolysis acidification-SBBR-activated carbonadsorption”, and it has a good effect on fracturing wastewater treatment, also providesa train of thought for studying the feasibility of wastewater.