A New Process Study On Treatment Of Shale Gas Fracturing Flowback Fluid

Shale gas is a new kind energy source with low-carbon and clean.The exploration and exploitation of shale gas can optimize the energy structure,ease the pressure to reduce emissions,protect the energy supply and improve energy efficiency.While large amount of water resources were wasted and a large number of shale gas fracturing flow-back waste liquid was produced in the process of exploiting shale gas.The shale gas fracturing flow-back effluent contains high concentration of salt,refractory organics,ammonia nitrogen,large amounts of bacteria,metallic elements and various chemical additives.The effluent may have a very bad impact on the surroundings if not disposed properly.The advanced ozone membrane reactor is created through coupling ozone oxidation and PTFE microfiltration membrane reactor,,which is an integrated device for recycling and decontamination,.The polyaluminium chloride?PAC?is selected as the flocculant for wastewater pretreatment,ozone is used to exterminate sulfate-reducing bacteria?SRB?,saprophytic bacteria?TGB?and iron bacteria?FB?.Simultaneously,the macromolecule organic matter is decomposed,and ammonia nitrogen is reduced..At last,use PTFE microfiltration membrane to further reduce the COD and salinity?SAL?of the flowback water.Meanwhile,the amount of Ca²⁺and Mg²⁺is decreased by a certain degree.The results showed that:?1?the optimal operating conditions of the device are as follows:?1?The optimal adding concentration of PAC is 400 mg/L in the flocculation sedimentation unit;?2?The residence time is 20 minutes as the ozone dosage is 3g/h in the ozone oxidation unit;?3?Using a PTFE microfiltration membrane with a narrow aperture can improve the treatment effect;?2?The ozone catalytic membrane reactor can effectively remove the COD,SS and SAL of shale gas Fracturing flow-back waste liquid,and the removal rate is 99.2%,66.99%and21.11%,respectively;?3?SRB,TGB and FEB of the PTFE microfiltration membrane can be exterminated effectively by ozone catalytic membrane reactor to below the detection limit;?4?The removal efficiency can reach 92.41%and 82.40%by PTFE microfiltration with average aperture diameter of 0.45?m and 0.80?m PTFE;?5?The microfiltration membrane unit of ozone catalytic membrane reactor can reduce the SAL,Ca²⁺and Mg²⁺of shale gas fracturing flow-back waste liquid by 21.11%,32.24%and 31.53%,respectively,and ozone oxidation unit can remove the ammonia by 22.47%;?6?GC-MS analysis shows that ozone can break up the unsaturated organic molecules,and decrease the molecular weight of organic macromolecule;therefore the toxicity of the shale gas fracturing flow-back waste liquid is reduced,which may improve the biochemical properties;?7?connecting PTFE microfiltration membrane in series can effectively improve the performance of water purification device,however,it will shorten the operation cycle of the device;?8?The ozone catalytic membrane reactor can effectively reduce the fetor of the wastewater;?9?After flushing polluted PTFE microfiltration membrane,use 400mg/L NaClO to backwash and the membrane flux recovers to nearly 100%.