Study On The Technology And Mechanism Of Oily Wastewater Treatment Under The DC Electric Field

With the widespread application of the enhanced oil recovery technology in the oil field,the water content of oilfield produced fluid exceeds the standard more and more seriously,of which the proportion of oil-in-water(O/W)emulsion has increased significantly.At present,the main treatment methods are air floatation and adding chemical reagents such as demulsifier,which will produce a large amount of sludge.These methods are not promote to cost savings,also not good for simplifying the treatment process.This technology used for oil-water separation showed many advantages,such as low energy consumption,no addition of chemical agents,no secondary pollution,high degree of device integration,which were beneficial to industrialization.So,it has a huge application prospect in the treatment of industrial oily wastewater.In this paper,firstly,O/W emulsified wastewater was prepared.The static and dynamic experiments of the self-made device were used to reveal the optimization of different parameters in the treatment process of DC electric field demulsification.There are electric field parameters,filler reinforcement and initial water quality of simulated wastewater.We pinpoint the optimal process parameters suitable for the device.For simulated emulsified wastewater with an initial oil content of 89.2 mg/L,the oil content of the effluent is less than 5 mg/L after treatment under optimal conditions,and the oil removal rate is as high as 95.3%.The results show that:increasing the electric field strength,reducing the size of the filler particles,and increasing the height of the filler are conducive to demulsification;the demulsification effect is best at pH=7;the higher the initial oil content,the higher the emulsion temperature,the worse the effect;the higher the salt content of the system,the larger the particle size of the oil droplets,the better the effect.The migration of emulsified oil droplets under the microscopic level was studied by using an electrochemical workstation and a biological microscope.The work shows the preliminary analysis and exploration of the mechanism of DC electric field demulsification.The experimental results of the migration of oil droplets under DC electric field show that the oil droplets began to migrate towards anode when the DC electric field was applied.However,it should be noted that the oil droplets did not coalesce during migration process.The migration rate of oil droplets was increased with the electric field intensity increasing.As the particle size decreased,the migration rate slowed down.The application of DC electric field could destroy the stability of surface charge structure of the oil droplets,resulting in the unbalanced distribution of surface charges,which led to the directional migration of the oil droplets.Specifically,the demulsification and separation mechanism of O/W emulsion can be described as:1)the oil droplets migrated towards anode driven by the electric field;2)demulsification and coalescence of the oil droplets occurred on anode surface;3)the oil droplets floated up caused by the gravity and separated from the water.