Research On Advanced Electrochemical Treatment System Of Oil-field Wastewater

Advanced electrochemical oxidation technology is one of most prospective method to treat oil-field wastewater, as long as it has a nature advantage of environmental compatibility. In electrochemical method, electron is used as reactant, and electric field is reaction dynamics. No additive chemical agent is needed, so secondary pollution can be avoided. It can combine with producing process directly while wastewater is being treated, and hazardous substance can be reduced in the producing process. However, there are many problems to solve in the application of electrochemical method in industry up to now. So three aspects of the subject is studied in this paper, including selection of anode material in electrochemical oxidation, the study on experimental circulating device of advanced electrochemical treatment of oil-field wastewater, and cleaning cathode surface fouling in electrochemical oxidation.In this paper, selection of anode material in electrochemical oxidation is carried out at first. Among graphite, BDD and Ti/RuO₂ electrodes, their different aspects is investigated comprehensively according to these anode material physical and chemical stability, oxidation power, current efficiency, generated material, economic value and so on. As the instability of graphite electrode and high cost of BDD electrode, Ti/RuO₂ electrode of better comprehensive property is selected ultimately. And it also used the characteristic of oil-field wastewater being rich in Cl- to product a large number of oxidative material, Fe2+ can change into Fe3+ to prevent metal pipe corroding and blocking as well as oxidation of organic matter in oil-field wastewater, and sterilization can be achieved.On this base, this paper develops experimental circulating device of advanced electrochemical treatment of oil-field wastewater. This system has such merits: it can treat oil-field wastewater circularly; velocity of water flow in and out can be regulated; oil from wastewater can be separated and recycled; pollution material can be drained out in and behind experiment; the process and change of experiment can be observed timely; corresponding electrode can be changed according to treating different kinds of wastewater.After using this system to treat oil-field wastewater, it is found that the current between electrodes is shown as a declining trend down to 0 A with the time increasing, because cathode surface is covered by white fouling layer. If it is not treated, the layer will cover the whole cathode. Electrochemical reaction will be blocked, and electrode will lose its activity. Therefore removing fouling scraper of cathode surface and exchange the electrode polarity two methods are added , and both of them can solve the problem of surface fouling well. The former which using the theory of physical friction is direct and simple, while the later which useing the theory of micro-loss electrode and air flotation is lower in cost and easy to process. So which of them is selected should accord to practical situation.