Test On Oilfield Wastewater Treatment

With the promotion and production of polymer flooding EOR technology in each big oilfield of our country, the oilfield produced more and more wastewater. The oilfield wastewater is a special kind of refractory organic wastewater. Use the traditional methods to treat oilfield wastewater can't achieve good treatment effect. The treatment process is pretreatment by iron-carbon micro electrolysis process-microbial treatment-advanced treatment. The toxicity of output of pretreatment by iron-carbon micro electrolysis process reduced significantly. In microbial treatment section, after the anaerobic microbial treatment, the macromolecular organic matter can be degraded into micromolecule, which can be advantageous to the subsequent aerobic microbial treatment. The aerobic microbial treatment can achieve good treatment effect. Then using the advanced treatment by H2O2/O3 to treat the oilfield wastewater. Finally the oilfield wastewater was treated with GAC. The GAC treatment has two sections. The first section is static adsorption and the second section is dynamic adsorption.The first section of the test is pretreatment by iron-carbon micro electrolysis process. The factors that affect COD removal efficiency including pH, reaction time, Fe/C, Fe/H2O were analyzed by orthogonal experiments and Single factor experiment. Orthogonal experiments were carried out to determine the order of different factors as follows:pH>Fe/H2O> reaction time>Fe/C; The optimal conditions:pH=4, Fe/H2O=1:6, reaction time=30min, Fe/C=3:1. Under optimal conditions, the average removal rate of COD, NH4+-N, PAM and oil are 53.1%,35.3%, 61.0%,38.3% respectively, the output of GAC dynamic adsorption's average COD, NH4+-N, PAM and oil are 153.2mg/L,18.1 mg/L,27.7 mg/L and 42.0 mg/L respectively.The second section of the test is microbial treatment. The optimal conditions of anaerobic microbial treatment:pH=7.4-7.6, reaction temperature=37?, HRT=20h. Under optimal conditions, the output of anaerobic microbial treatment's average COD and NH/-N are 116.9mg/L and 22mg/L, the average and maximum removal rate of COD is 25.7% and 27.9% respectively, and the average and maximum growth rate of NH/-N is 18.4% and 20% respectively. The average removal rate of PAM and oil are 10.3% and 21.0% respectively, the output of anaerobic microbial treatment's average PAM and oil are 24.8 mg/L and 33.2 mg/L respectively.The optimal conditions of aerobic microbial treatment:pH=8-8.2, reaction temperature=34?35?, HRT=18h. Under optimal conditions, the output of aerobic microbial treatment's average COD is 57.8 mg/L, the average and maximum removal rate of COD are 51.3% and 55.2%. The average removal rate of NH4+-N, PAM and oil are 93.5%,30.9%,58.0% respectively, the output of GAC dynamic adsorption's average NH4+-N, PAM and oil are 1.4 mg/L,17.1mg/L and 13.9mg/L respectively.The third section of the test is advanced treatment. The optimal conditions of H2O2/O3: dosage of H2O2=0.4 mL, pH=8, reaction temperature=20?, reaction time=20min. Under optimal conditions, the average removal rate of COD, NH4+-N, PAM and oil are 29.2%,32.2%,82.8%, 82.1% respectively, the output of GAC dynamic adsorption's average COD, NH4+-N, PAM and oil are 40.9mg/L,0.97 mg/L,2.90 mg/L and 2.50mg/L respectively; The optimal conditions of GAC static adsorption:dosage of GAC=30g, pH=7, reaction temperature=30?, reaction time=45min. Under optimal conditions, the average removal rate of COD, NH4+-N, PAM and oil are 63.8%,67.7%,84.1%,83.0% respectively, the output of GAC dynamic adsorption's average COD, NH4+-N, PAM and oil are 22mg/L,0.45mg/L,2.72mg/L and 2.36mg/L respectively; When pH=7, reaction temperature=30?, influent flow rate=0.5m/h, the average removal rate of COD, NH4+-N, PAM and oil are 67.0%,73.9%,84.5%,83.6% respectively, the output of GAC dynamic adsorption's average COD, NH4+-N, PAM and oil are 19.1mg/L,0.4mg/L,2.65mg/L and 2.27mg/L respectively. The GAC adsorption can achieve better treatment effect than H2O2/O3. The GAC dynamic adsorption can achieve better treatment effect.In a word, using pretreatment by iron-carbon micro electrolysis process, microbial treatment and advanced treatment to treat oilfield wastewater can achieve better treatment effect of COD and NH4+-N. The output had no secondary pollution and the cost reduced. Therefore, this technology has good application prospect.