Study On Wellsite Wastewater Treatment Technology

Wellsite wastewater is a special kind of wastewater generated during drillingoperations in the oil and gas field wellsite, mainly by the sewage and waste drillingfluid, the nature and hazards with revelant to the type of drilling fluid and treatmentagent comprising. In the process of oil and gas development in Northern of Shaanxi,oil and gas companies adopted a number of measures put into production and yield,generated a lot of wellsita sewege, wellsite wastewater will be a significant increase, adrilling well generated drilling sewage300⁵00m3, waste drilling fluid400⁷00m3.According to the survey, the oil and gas fields in Northern of Shaanxi, the wellsitewastewater produced annually a total of6¹0million m3.In this thesis, reviewed the wellsite wastewater treatment overview, disscussedand summarized the wellsite wastewater treatment technology status and developmenttrend, and analysised the coagulation、advanced oxidation and activated carbonadsorption mechanism of the wellsite wastewater treatment.Fist, the coagulation pretreatment on the wellsite wastewater, and Fentonoxidation treatment, finally, use the activated carbon adsorption depth treatment. Bysingle factor analysis of the experimental, get the relationship of the factors of thecoagulation、advanced oxidation、activated carbon adsorption process and the CODremoval efficiency, disscussed the types and dosage of organic flocculants, the typeand dosage of inorganic flocculants, pH, pharmaceutical dosage effect on coagulationresult, and the Fe²⁺/H₂O₂（molar ratio）, pH, reaction time effect on Fenton oxidationtreatment, the activated carbon dosage, degree of adsorption equilibration time and pHeffect on activated carbon adsorption treatment, explore the mechanism of action of theimpact of various factors on this basis. Through experimental studies, determine the optimum conditions of the wellsitewastewater treatment program and its process operation. The process is divided intothree steps:①Coagulation②Fenton oxidation③activated carbon adsorption. Whichcoagulation treatment: PAC dosage of2600mg/L and the PAM dosage to15mg/L,pH=8.0, feeding order first PAC added PAM, the settling time of30min;Fentonoxidation treatment conditions: H₂O₂/Fe²⁺（molar ratio） of9:1（FeSO₄7H₂O increasethe amount to800mg/l, the amount of H₂O₂dosage of2.2mg/L）, pH=3.5,reactiontime of90min;Activated carbon adsorption process: activated carboninvestment plus the amount of50mg/L, adsorption balance time120min, pH=3.0.By “coagulation-Fenton oxidation-activated carbon adsorption” treatment under theoptimum operating conditions, COD removal efficiency in the water up to99%,turbidity and color also reduced significantly, water quality indicators have reached thelevel of emission standards in the Integrated Wastewater Discharge Standard（GB8978-1996）.