Research On Dissolved Ozone Flotation Treatment Characteristics Of DOM In Secondary Effluent Of Drilling Wastewater

A large amount of waste water will be generated during the oil and gas development process,and the current mainstream response is to establish a centralized treatment plant to dispose of it.Although the drilling wastewater after conventional centralized treatment can meet the reinjection standard,it will still cause irreversible damage to ecologically fragile areas if a large amount of discharge is carried out.Therefore,it is urgent to develop appropriate advanced treatment technologies.In this regard,this study analyzed and characterized the characteristics of the dissolved organic matter in the secondary effluent of a drilling wastewater centralized treatment plant,and proposed a suitable integrated ozone-air flotation advanced treatment process,and proved the best working conditions and reaction mechanism.And carried out large-scale application on the spot.The main research contents and results of this paper are as follows:Through the classification and characterization of the dissolved organic matter in the secondary effluent of the drilling wastewater centralized treatment plant,the composition characteristics of the dissolved organic matter in the secondary effluent are proved.The results show that the dissolved organic matter is mainly hydrophobic acidic organic matter(HOA)and hydrophobic neutral organic matter(HON).Humus substances are the main components of the above two types of dissolved organic matter,mainly including alkanes,amines,aromatics,Alcohols,aldehydes,carboxylic acids,lipids,and other organic substances that may contain carbon-carbon double bonds,the molecular weight is mainly distributed in the range of 500-1000 Da.Proteins are the main components of hydrophobic alkaline organics(HOB)and hydrophilic organics(HI),mainly including alcohols,carboxylic acids,lipids and amine organics,and their molecular weights are mainly distributed in the range of 500-1000 Da.Through laboratory beaker experiments and simple reactors to simulate the treatment process of the integrated ozone and air flotation process,the good applicability of the technology to the secondary effluent of drilling wastewater was further verified,and the best working conditions were proved.In the static beaker experiment,the best removal effect can be obtained when the dosages of PAC and PAM are 550 mg/L and 2.5 mg/L,respectively.After adding ozone to form an ozone-coupled coagulation reaction system,the ozone dosage is 35 mg/L to reach the optimal value.When performing feasibility verification in a simulated reactor,the treatment capacity is set to 4 m~3/h.At this time,the device can remove most of the organic matter and suspended particulate pollutants in the influent water,and the COD and turbidity in the effluent can be respectively It is reduced to 220 mg/L and below 2 mg/L.By grading and analyzing and characterizing water samples at different processing stages in a simple simulation device,the migration and transformation laws of dissolved organic matter in the integrated ozone-air flotation process are studied.The results show that HOA and HON in the secondary effluent have an excellent removal effect in this process.Among them,the large-chain aromatic hydrocarbons in the HOA component are more prone to 1,2,4-tri-substitution and 1,3-di-substitution,so that the chain scission is an organic substance with a smaller molecular weight.The large amount of carbon-carbon double bond-containing organics in the HON component are more likely to be chain-scissioned to generate small molecular weight organics containing hydroxyl and carboxyl groups.Organics containing CO bonds in HOB and HI are more likely to be oxidized and broken into small molecular weight organics such as alcohols,aldehydes and carboxylic acids,and these two types of components contain less aromatic hydrocarbons,and almost no substitution on the benzene ring occurs.reaction.After exploring the water quality characteristics,verifying the process feasibility and studying the reaction mechanism,the research group applied the developed technology to the actual engineering of drilling wastewater advanced treatment,and designed and built a production device with a treatment capacity of 50 m~3/h.After long-term stable operation,the removal rate of chroma,COD,turbidity and suspended solids by this process can reach 25.4%,49.9%,95%and 96%,respectively.The results of this research have enriched the advanced treatment technology of drilling wastewater and provided strong support for the development of oil and gas field production and development.