Application Study On Neutralization-coagulation And NaCIO Oxidation For Treatment Of Oilfield Fracturing Wastewater

In last several years, petrochemical industry of our country was developed a lot,however, serious environmental pollution comes with gratifying results. Fracturingwastewater which will flow back to the ground is high COD_cr, chroma, viscosity,stability and refractory for adding in lots of additive. The surrounding environment,especially crops, surface water and atmospheric environment will be polluted heavily iffracturing wastewater goes without treatment.The characteristics of the oilfield fracturing wastewater is analyzed firstly in thethesis, then the combination process “Neutralization—Coagulation—NaClO oxidation—Micro-electrolysis” comes out to treatment the wastewater after lots of literaturereading and experiments. Finally, this process is applied to treatment fracturingwastewater of Changqing, and the operating conditions of each sub-process areoptimized. The result shows the combination process has a good performance.The followed conclusions is supported by experiments:the best effect will begotten by neutralization coagulation experiment when dosing8g/L of Ca（OH）₂,0.6g/LPAC and3mg/L PAM, the removal rates of turbidity and oils are very high,89.2%and83.6%, respectively, but lower removal rate of COD_crin the situation, only37.1%.Italso shows that the dosages of Ca（OH）₂, PAC and PAM are different in the differentfracturing wastewater; The highest removal rates of turbidity and oils,56.7%and47.7%, respectively, will be gotten by NaClO oxidation experiments when pH=3,dosage of NaClO is0.8g/L and oxidation time lasts30minutes; The removal rate ofturbidity will get45.1%and COD_crwill get60.8%after fracturing wastewater ishandled by self-made micro-electrolysis reaction device for30minutes when pH=3inmicro-electrolysis experiment; The removal rate of COD_crin micro-electrolysis is thehigest compared to Neutralization-coagulation and NaClO oxidation; After fracturing wastewater is handled by the whole combination process, the removal rates97.6%and98.0%for turbidity and oils will be reached, COD_crwill be reduced from4937mg/L to637mg/L, the removal rate is87.1%.The research showed that the combination process “Neutralization—Coagulation—NaClO oxidation—Micro-electrolysis” has played a positive and effective role in thetreatment of oilfield fracturing wastewater, wastewater quality has been improvedsignificantly and the experiment is verified to be feasible.