At home and abroad in recent decades, a variety of "breaking" method done a lot of research. Wherein the chemical methods are: acidification, salting, acidification coacervation, coacervation, demulsifiers method, physical method electrolytic treatment method, flotation method, high gradient magnetic separation method, an ultrafiltration method. There are physical and chemical methods, such as chemical demulsification + electrolysis flotation method. These methods have advantages and disadvantages for different emulsion wastewater treatment.

1. ultrafiltration (Ultrafiltration)
Abroad in the late 1960s began to ultrafiltration device used in industrial systems, our country since the 1970s started research work in this area, but whether at home or abroad, the ultrafiltration device used in wastewater treatment works is not universal, which is ultrafiltration device relatively expensive price, technical complexity to some extent. With the development of membrane technology, the low pressure, at room temperature, single phase, centralized control system, easy management superiority is increasingly recognized by users.

1.1 Principle of ultrafiltration
Ultrafiltration principle is to use the larger pores semipermeable membrane, using a cross-flow manner, in the case of a pressure differential and flow turbulence, waste most polar molecules through a semipermeable membrane, while all non- polar molecules (such as colloidal particles) and higher molecular weight substances can not be trapped by a semipermeable membrane, so that the waste water purification. Cross-flow filtration is a continuous filtration process, the input flow parallel to the film, while the vertical portion of the liquid through the permeable membrane, the pressure differential across the membrane of the osmotic pressure. Liquid cross flow caused by turbulence, the particles can flush the membrane surface, reducing pollution levels membrane surface. Ultrafiltration separation of fine particles mainly at the molecular level, the size of the diameter of 0.01 ~ 10mm, a molecular weight generally greater than 500, such liquid osmotic pressure is small, and therefore the use of smaller operating pressure, can generally 0.1 ~ 0.5Mpa. E.g., the use of semi-stable ultrafiltration treated oil in water type emulsion wastewater, can be cutoff ultrafiltration membrane having a molecular weight of 15,000 to 20,000, as mentioned above the operating pressure of 0.35Mpa, purified water permeability was ~ 340L / m2 ˙h, the transmittance of the emulsion was 46L / m2˙h.

1.2 ultrafiltration membrane material
Since ultrafiltration is carried out at both sides of the ultrafiltration membrane, ultrafiltration membrane material will therefore directly affect the ultrafiltration effect. Ultrafiltration membrane was first organic film from the beginning, in the early 1960s developed a cellulose acetate membrane, the membrane resistance, PH value in the range of 3 to 10, the maximum operating temperature of ~ 40OC, good stability, through a large amount of cleaning cycle is generally 5 to 10 days, longer life of the membrane. Ultrafiltration of the late 1980s and the introduction of a cold rolling mill is used in this membrane, so far, only the replacement of two-thirds of ultrafiltration. Later, people developed a polyamide film, PH expanded tolerance range of 2 to 13.5, the maximum operating temperature of ~ 57OC. After years of research, it was discovered that the ideal ultrafiltration - charged sulfonated polysulfone membrane and a polyvinylidene fluoride film, the film surface with a negative charge, itself can adsorb (or rejection) of some inorganic ions to achieve electrical balance, it has good anti-pollution ability. These emulsions rejection organic film is generally> 99.8% and a flux of <50L / m2˙h, membrane tube life is generally three to five years, but the high cost, generally 33 to 35 yuan / m2, not easy to clean clean, oil easily attached to the film, must use a sponge ball or fiber ball was wiping clean.

Since the organic film prices are too high, and the organic film has no heat, wide pore size distribution, low mechanical strength, easily hydrolyzed and other shortcomings, people began to study low-cost, longer life, better durability of the film material. In the late 1980s to the 1990s, and finally developed an asymmetric membrane inorganic ceramic materials (zirconia, alumina, iron oxide, etc.) prepared by the high temperature treatment - inorganic ceramic membrane. Ceramic membrane has excellent chemical stability, as well as acid, alkali, organic solvents, high temperature, anti-microbial ability, PH value tolerance range of 0 to 14, in a temperature range of 0 ~ 300OC, operating pressures up to ~ 8bar. Its rejection emulsion is generally> 99.9% and a flux of ~ 100L / m2˙h, membrane tube life is generally 3 to 10 years, but the cost is not high, generally 6 to 10 yuan / m2; Furthermore, the ceramic membrane cleaning are more likely, oil is not easy to adhere to the membrane. The disadvantage is that the ceramic membrane tube film complex process, especially the difficulty small pore membrane preparation, brittle and poor flexibility, impact resistance is poor, transport and operation brittle.

At present, there are reported to be hydrophilic fine inorganic ceramic material (Al2O3) doped into the polysulfone to prepare a composite membrane prepared in the same process and that the organic film composite membrane, the process is simple, easy to operate, and an organic common advantages of film and the inorganic film. Such composite membranes can be prepared in a variety of carriers, it can be made into various forms of membrane module. Adding an inorganic ceramic material can make the ceramic film composite membrane performance is almost the same, while avoiding the disadvantages of brittle ceramic membrane. It reported that the highest porosity of this composite film can reach 81.3%, the maximum flux at 0.1Mpa operating pressures up to 124.4L / (m2˙h).