Research On The Membrane Fouling Causes And Cleaning Methods Of Plate Ceramic Membranes On The Treatment Process Of The Oil

Because of the simple process and the good treatment effect,membrane treatment technology become one of the new technologies in oil extraction wastewater treatment field,and attract more and more attention.The previous studies using ceramic plate membrane filter device for oil extraction wastewater treatment showed that treatment effect is good,and all indexes of injection water are better than the A1 class standards in SY5329-94?SS<1mg/L,oil<5mg/L?.However,membrane fouling problem has been accompanied by the entire process,and it has become the constraint of inorganic ceramic membrane technology used in the practical application and development treating of oil extraction wastewater.In order to study the causes of membrane fouling and find optimal cleaning methods,we can observe the pollutants on membrane surface through the microscopic methods,to analyze pollutants composition.On this basis,we can find the best cleaning agent,so that the membrane flux can be restored.Firstly,we defined membrane fouling of the ceramic plate membrane used in the oil extraction wastewater treatment.Usually we regard the membrane surface changing from white to yellow,transmembrane pressure increasing rapidly and the membrane flux decline as ceramic plate membrane is polluted,but the definition standard is too vague.Thus this test regarded the transmembrane pressure of a small amount of bubbles appearing in the suction pipe of the suction pump as membrane fouling standard,that is whenthe membrane flux is among 15⁴5 L/?m²·h?and the transmembrane pressure greater than or equal to 0.03MPa,the membrane is polluted and needs for cleaning.Secondly,this experiment using the scanning electron microscope?SEM?and atomic force microscope?AFM?to observe ceramic plate membrane surface before and after membrane fouling.The blank membrane surface can be clearly observed that pores are even and fine.The polluted membrane surface can be clearly observed that pores are blocked and the surface is covered with paste.We analyzed causes of membrane fouling along the filter layer structure?from outside to inside?:concentration polarization in adhesion layer,cake layer on the membrane surface,membrane pore clogging in the separation layer.The ICP and GC-MS data showed that the metal element content of the membrane surface pollutants is less,so it is not the most important factor of membrane fouling.Causing membrane obstruction and membrane flux decline is mainly oil and other organic pollutants,especially petroleum hydrocarbons,ethers and alcohols.Membrane cleaning test regards transmembrane pressure during the operation as evaluation standard.We researched on the membranes immersed in different cleaning agents how fast the membrane fouling is when it is put into used.After observing changes of the transmembrane pressure over time,we get the best cleaning agent is0.1mol/L of HNO₃,and immersed for 12h can meet recovery requirements of membrane flux.This is because acid can make part of the organic pollutants hydrolysis reaction.And it can react with carbonates and alkaline substances in pollutants and make pollutants desorbed from the surface of the membrane.Ceramic plate membrane fouling in the processes of oil extraction wastewater treatment is inevitable,but can be reduced by a number of ways.Taking prerequisite for energy into account,we can adjust the aeration,membrane flux,temperature,etc.of devices to slow down pollutants attached to membrane surface and reduce membrane fouling rate.We can also slow down the process of membrane fouling by adding coagulants to main reactor and setting an electrolytic flotation device at the bottom of the main reactor to extend membrane operation period.