Research On The Pretreatment Technology And Determination Of The Biodegradability Of The Polymer Flooding Oil-extraction Wastewater

At present,the oil-extraction industry has entered the three stage of oil production.Polymer flooding technology was used to improve oil extraction,which plays an irreplaceable role in stable production of crude oil.The polymer in polymer flooding oil-extraction wastewater is mainly polyacrylamide?PAM?which increased gradually as well as the viscosity.The biodegradability of polymer flooding oil-extraction wastewater is poor and the component is more complex and the treatment processing is difficult.With the more strict requirements of the environmental protection work and more attention to the environment,the treatment situation of polymer flooding oil-extraction wastewater is quite urgent.In order to reduce the pressure of follow-up biochemical treatment and the organic matter in the actual oil production wastewater,it is necessary to improve the biodegradability of polymer flooding oil-extraction wastewater.In order to reduce the effluent COD and improve the biodegradability of the polymer flooding oil-extraction wastewater,it has been pretreated by O₃/UV,O₃/H₂O₂,UV/H₂O₂ and H₂O₂/O₃/UV process.Several biochemical characterization methods were used to reflect the biodegradability of PAM wastewater,such as BOD₅,the aerobic respiration rate and Zane ·Huilunsi experiment.The results reveal that O₃/UV,O₃/H₂O₂,UV/H₂O₂ and H₂O₂/O₃/UV can improve the removal efficiency of COD and PAM of the wastewater more obviously compared with ozone alone,and H₂O₂/O₃/UV performed best.The improvement of the biodegradability of the wastewater by O₃/H₂O₂ was the most obvious.Under the pretreatment of O₃,O₃/UV,UV/H₂O₂,O₃/H₂O₂,H₂O₂/O₃/UV,B/C of the polymer flooding oil-extraction wastewater were increased to 0.011?0.092?0.13?0.175 and 0.22.Taking practical engineering application into account,under the following conditions:pH = 8.01,O₃ concentration was 19.7 mg/L,reaction time was 30 minutes at 18 W UV lamp irradiation,B/C was up to 0.092 by O₃/UV process.Under the following conditions:pH = 7.0,dosage of H₂O₂ was 2mL/L,reaction time was 30 minutes,B/C was up to 0.13 by O₃/H₂O₂.Under the following conditions:O₃ concentration was 19.7 mg/L,reaction time was 30 minutes and amount of mole ratio of O₃ and H₂O₂ was 0.3,B/C was up to 0.175 by O₃/H₂O₂ process.And under the following conditions:pH=8.53,O₃ concentration was 25 mg/L,eaction time was 30 minutes and amount of mole ratio of O₃ and H₂O₂ was 0.5,B/C was up to 0.22 byH202/O₃/UV.The influential factors during determination of BOD₅ need to be controlled strictly:before the determination of BOD₅,the pH of the solution need to ajust between 6-8.Acid or alkali conditions can lead to BOD₅ value smaller;the temperature had great influence on BOD₅,the microbial activity increased with the increase of temperature,so the temperature need to be controlled on 20±1? during BOD₅ measurement;phosphate buffer solution was the most necessary to BOD₅ measurement,ferric chloride solution was the least necessary to BOD₅ determination;different sources of inoculums also influenced BOD₅ value,which HACH supernatant had bigger BOD₅ value while the river water supernatant were similar to Changqiao water purification plant supernatant;copper ion,nickel ion and pentachlorophenol had negative effect on BOD₅ measurement;with the increase of the concentration of ammonium chloride,BOD₅ value of glucose glutamic acid standard solution increased gradually,attributing to the effect of nitrification.By adding allyl thiourea as a nitrification inhibitor,the interference of nitrification effect on BOD₅ measurement could be eliminated.The biodegradability of the polymer flooding oil-extraction wastewater pretreated by O₃/H₂O₂ was investigated through the aerobic respiration rate and Zane-Huilunsi experiment.The results reveal that macromolecule of polymer flooding oil-extraction wastewater can become small molecules by O₃/H₂O₂.The biodegradability of oil-field wastewater was obviously increased by oxidation pretreatment,which could reduce the pressure of follow-up biochemical treatment.By comparing BOD₅ measurement by dilution inoculation method,BOD₅ online monitoring method,aerobic respiration rate method and Zahn-Huilunsi experiment,the biodegradability of wastewater was characterized.Dilution inoculation is the most classic and widely method,but the operation is complex;BOD₅ online monitoring method based on dilution inoculation method is simply used with automatic detection,both dilution inoculation method and BOD₅ online monitoring method are in the range of measurement error,which may be subjected to the sensitivity of the instrument and the precision and human errors.Aerobic respiration rate is creative but not stable,in which certain kind of activated sludge is required,and it is suitable for wastewater analysis with specific pollutants;Zahn-Huilunsi experiment needs 28 d which is quite time-consumed and can't be used for quick analysis.