The application of ceramic membrane separation technology in edible oil wastewater treatment

1.The introduction of membrane filtration technology

Membrane filtration is a hot technology in the treatment of industrial wastewater at home and abroad. Compared with other filtration and separation technologies, membrane filtration technology has the advantages of low energy consumption, high separation efficiency, strong reliability, small equipment area and high degree of automation control. The membrane filtration technology is used to treat all kinds of oily wastewater, which does not consume chemicals and produce new pollution during normal operation. Polyacrylonitrile (Pan), polysulfone (PSF) and cellulose acetate (ACF) membranes have been used for the treatment of oil-bearing wastewater (LLJ) in China. However, these membranes are all organic membranes, which have disadvantages such as poor chemical stability, easy aging, short service life (only 2-3 years), high replacement cost, poor resistance to high temperature, acid, alkali, organic solvents, and limited application scope and operating conditions. At present, the trend of using inorganic ceramic membrane to treat all kinds of oily wastewater has appeared at home and abroad. Compared with the organic membrane, the inorganic membrane has the advantages of high temperature resistance, acid alkali resistance and organic matter corrosion resistance, high mechanical strength, long service life (more than 5 years), narrow pore size distribution, high oil cut-off rate and good operation stability. When the composition and concentration of oily emulsion wastewater change, the water quality of permeate is little affected. In addition, membrane bioreactor (MBR), which is formed by the combination of inorganic ceramic membrane module and wastewater biochemical treatment device, also shows good treatment effect in oil-bearing wastewater treatment, and becomes a new development direction of oily wastewater treatment.

2. Principle of inorganic ceramic membrane filtration technology for oily wastewater treatment

In the treatment of oily wastewater by inorganic membrane filtration, under a certain pressure, the oil droplets and suspended solids are intercepted by the membrane pore by using the surface tension of the oil. Inorganic membrane is a polar membrane with strong hydrophilicity and oil repellency. It can form a gel layer in the filtration process. Therefore, in practical filtration, oil droplets far smaller than the pore size can be retained, resulting in very low oil permeation concentration. The oil is continuously concentrated in the circulating tank, and the small molecular substances and water molecules dissolved in water become the osmotic solution through the membrane pore. The oil content in the permeate is very low, usually less than 1% of the treated wastewater.

3. The characteristics of inorganic membrane filtration technology

1. The working modes of inorganic ceramic membrane filter for oily wastewater include full filtration (cross flow filtration) and cross flow filtration (tangential flow filtration)

2. Inorganic membrane filtration is characterized by simple operation and easy automation

3. The on-line instantaneous recoil technology can reduce the membrane surface pollution and prolong the service life and cycle

4. The membrane flux is large, the filtration area is reduced correspondingly, and the equipment occupies less space, only 2-3m2 is needed.