Oily wastewater treatment process and key technologies

Since entering the new century, with the rapid improvement of the market economy in our country, all walks of life have achieved very rapid development, and the living standards and quality of life of urban residents have also been significantly improved. However, at the same time, the ecological environment in our country Also suffered serious damage, all kinds of pollution sources continue to erode our ecological environment. Among them, water pollution is a complex subject with many pollution sources. In China's water pollution treatment, the treatment of oily wastewater is a very difficult task. We should fully analyze the sources of oily wastewater and analyze its harm , Clarify the work process of oily wastewater treatment, so as to formulate a scientific and rational treatment measures. This paper analyzes the sources and harms of oil-contaminated water, the technological process of oily wastewater treatment and the key technical methods of oily wastewater treatment in detail, and then analyzes in detail the oily wastewater treatment in our country.

1 oily wastewater sources and hazards

1.1 source of oily wastewater analysis

The source of oily wastewater in our country is very wide. Oily wastewater is produced in the process of iron and steel refining, industrial production, petroleum exploitation and pesticide and food processing and production, and these oily pollutants mainly exist in four forms , Respectively, dissolved oil, dispersed oil, slick oil and emulsified oil.

(1) petrochemical industry. In China's petrochemical industry, from the initial mining to the final transport and consumption, almost any stage will produce oily wastewater. With the rapid development of science and technology in our country, the tertiary recovery technology in our country has also been widely used , Which improves the effect of flooding but also complicates the composition of the sewage.

(2) Chemical Pharmaceutical Engineering. Its main source is oily wastewater with high concentration process. During the manufacturing process, a large amount of oily wastewater will be produced in the later stage due to the large amount of water and lubricating oil used in the raw material reaction, product separation and raw material pretreatment.

(3) metal smelting industry. In the process of smelting metal, whether it be the material in contact with the oil or the equipment in contact with the oil, we are about to cool, clean and lubricate it, and the lubricating oil may come into direct contact with it, so that oily wastewater .

(4) food processing and production. In our country's food processing and production process, equipment cleaning and machine lubrication and other stages have to produce oily wastewater.

1.2 oily wastewater hazard analysis

(1) oil-contaminated water pollution of drinking water sources. If our daily source of drinking water is polluted by oil-contaminated water, not only human beings and animals will be infected with the disease, but they may even cause food poisoning. The oil-contaminated water is also a certain amount of carcinogenic substances, so it is possible Will increase the incidence of cancer in areas contaminated by oily wastewater;

(2) oily wastewater discharged into rivers and lakes. The density of oil-contaminated water is lower than the density of normal pure water, so once oily wastewater is discharged into rivers and lakes, it will adhere to the surface of the water, and the atmosphere and water can not be exchanged normally. The oxygen content in water Declining, then the aquatic plants can not grow normally, the quality of water bodies are seriously affected, significantly reducing the value of water resources utilization;

(3) oily sewage into the soil. If oily wastewater is used as irrigating water to irrigate the soil, the oily soil will deposit on the surface of the crop, the soil will not be able to exchange effectively with the outside air, and the soil will be metabolized more slowly, thus affecting its normal growth and may even result in The death of crops, if the oil-containing crops are consumed by humans, can also be detrimental to our health.

2 oily wastewater treatment process

Under normal circumstances, when we deal with the sewage, the process of the first oil-water separation process for oily wastewater, and then by coagulation or floating method to further separate the oil and water, then we should be quantitative The addition of PAM and PAC guarantees the full occurrence of the flocculation reaction and the coagulation reaction. This process avoids the occurrence of clogged oil treatment devices, and the oil removal performance of each device can also be fully utilized. When the oily wastewater enters the high efficiency combined flotation, a large amount of SS and oil have already been removed. At this time, we should measure the water quality first. If the water quality still does not meet the standard, then we should use activated carbon filter tank or quartz Sand filter tank filter to ensure that they meet the quality standards before discharge. The main purpose of our first oil-water separation is to reduce the degree of emulsification of oily wastewater. If it is oily wastewater with high solidification point and large particle size, then there should be insulation and heating equipment. If the difference in oil-water specific gravity is small Of oily sewage, it should be used filter device. When choosing materials for the treatment plant, we should take full account of the temperature parameter. In the efficient combination of aerosol scum discharge to the sludge storage tank, driven by a pneumatic diaphragm pump to filter the filter press dewatering, and finally its external processing.

3 oily wastewater treatment of key technical methods

3.1 coagulation method. This method is mainly aimed at the separation of tiny suspended particles and gummy particles in oil-contaminated water. First, we should add a certain amount of chemicals to the oil-contaminated water to allow it to undergo a sufficient chemical reaction and then Gradually condensed into a flocculent or a relatively stable mixture; then, we will join the coagulant into the sewage, so that the original colloidal particles in the sewage is no longer a negative charge, but was a Neutral, flocculent polymer or a stable mixture will slowly sink. In the actual process, we often use ferric chloride, basic alumina, aluminum sulfate and ferrous sulfate and other coagulants, accelerated clarification tank is usually used as a structure.

3.2 filter method. The so-called filter means that under the action of the filter will intercept particulate matter in oily wastewater, so that oil and water separated to achieve the desired purification effect. Under normal circumstances, the filtration method should be the next method of coagulation and floatation method of treatment, the formation of polymer or a stable mixture, the use of filtration can remove the gummy oil stains. With this method of treatment, the oil content of the final treated oily wastewater does not exceed 10 mg / l, and pressure and conventional fast filters are often used as structures. The use of filtration management process is a certain degree of difficulty, should be hot water backwash or air reverse aeration operation, otherwise it is prone to filter clogging problems.

3.3 flotation method. This method is mainly used in the removal of oily wastewater emulsions and smaller oil particles in the work, using this method after the oil-containing sewage treatment oil content does not exceed 30mg / l, its working principle is: first to oily wastewater irrigation Into a certain amount of air, so there will be a large number of bubbles in the sewage, bubbles will also float up, then formed a bubble, water and oil together form a non-uniform system, the bubble will be closer to the density of the oil Combined with the gradual upward movement, also achieved the effect of oil-water separation, according to the bubble generated by the different ways, we can float the law can be divided into the following categories:

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