Abstract

Oilfield waste water treatment is the key procedure in the oil production process. This article introduce the characteristics of oilfield waste water, detailed describe the current waster water treatment technology and its advantages and disadvantages and analyze the development tendency of waster water treatment. Oilfield Sewage is a complex liquid mixture, whose main ingredients are water, oil, soluble gases, suspended solids, electrolytes, bacteria and various oilfield chemical additives. Oilfield waste water containing oil, direct discharge will cause oil pollution; oilfield waste water or salts of acidic gas pipeline will accelerate corrosion of equipment; oilfield waste water suspended solids can clog formation; oilfield sewage bacteria in industrial pipeline corrosion, clogging pipes, and deterioration of water quality. On the rational use of oil field waste  water treatment technology is critical.

1. Oilfield waste water treatment

Oilfield waste water treatment method according to the principle can be divided into physical, chemical, physico-chemical and biological methods.

(1)  Physical method

Gravity sedimentation: gravity sedimentation basic principle is to use oil and water two-phase density different size, so that the mixture of oil and water relative motion in the gravitational field, and ultimately oil and water separation. Gravity setting equipment for gravity setting tank for pre-treatment of oilfield waste water.

Coarse-grained method: coarse-grained means when oilfield waste water cross the chemical control tank, coarse material make the oil in the oilfield waste water based diameter from small to large process. Coarse graining method is mainly degreasing process before use in gravity sedimentation.

Filtration: The filter method is the use of porous media to remove the oilfield sewage solid impurities, commonly used in the last paragraph of the treatment of sewage. Oilfield wastewater treatment filter used gravit filter and pressure filter, the current widespread use of a pressurized oil filter.   

(2) Chemical method

Flocculation process: chemical flocculation method refers to the role of flocculant, oilfield waste water and fine colloidal suspensions and electrostatic adsorption or bridging, the resulting floc is removed. Flocculation process as a pre-treatment technique is widely used in major oil fields, often in conjunction with the flotation method.

Chemical transformation method: chemical conversion method is the use of chemical agents dissolved in oil sewage inorganic and organic chemical poisoning or toxic reactions to the micro-transition, the resulting material is stable and easy to separate from the wastewater.

(3) physical-chemical process

Adsorption: adsorption method is the use of molecular attraction or bond strength to make the dissolved oil and other organic pollutants in the oilfield enrichment on the porous solid sorbent surface, so as to achieve the purpose of separation. Adsorption method commonly used in their treatment of oilfield waste water.

Flotation: flotation method (also known as flotation method) is the use of oilfield waste water hydrophobic particles to pass into the water bubbles that adhere to the bubbles pollutants in the sewage, because bond density is less than water, with bubbles floating, floating pollutants to the surface, forming a three-phase foam layer of the bubble, water and contaminants formed foam layer to collect pollutants and water separation. Flotation method widely used often in combination with the use of flocculation process.

(4) biological method using microbial degradation of organic matter to inorganic to metabolize oil field sewage disposal. Depending on the type of microorganisms can be divided into aerobic and anaerobic methods, including activated sludge, biofilm, oxidation pond method, BAF law.

2. Oilfield waste water treatment technology

Future trend of oilfield waste water treatment technologies focused on the following four areas:

First, the research and development of energy efficient waste water treatment process, such as joint classification using a variety of methods, five full play to the advantages of each processing unit to improve the efficiency of oilfield waste water treatment.

The second if to strengthen the small-scale sewage treatment equipment research and development, such as jet flotation machine, dynamic hydrocyclone etc.

Third, development new oilfield waste water treatment chemicals, such as how to develop to the multi-functional and spectrum aspect.

The fourth is to strengthen the research of oilfield waste water oil removing mechanism, and develop new technology. 

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