Investigation On The Mechanism And Experiment Of Electroflotation For The Treatment Of Special Wastewater

Electroflotation is a process of generating, via electrolysis, a controlled cloud of charged hydrogen and oxygen gas bubbles, which rise through the wastewater solution and attach themselves to insoluble contaminant particles. The foamy layer that gathers at the surface is then skimmed off by mechanical or other means. The electroflotation units are small and compact, cost effective without secondary pollutants, and require less maintenance and running cost than other flotation units.Oily wastewater, as one kind of special waste water, has been studied for decades. The oily emulsion wastewater is a typical oily wastewater, which is difficultly biodegraded and can induce heavy environmental pollution. Till now, it is very difficult to be treated with conventional methods.The electroflotation for oily emulsion wastewater was studied with the reactor designed by myself. The study on the oil and COD removal efficiency of the simulated and practical wastewater by electrocoagulation and coagulation-electroflotation were carried out on the graphite and aluminum electrodes, respectively. The factors affecting the removal efficiency were analysed with orthogonal test and other methods. The conclusions are as follows:The key factors affecting the oil removal efficiency during the coagulation-electroflotation process are as follows: pH value>electrocoagulation time>electrodes gap>current density. The optimum operating condition was as follows: current density was 15.6A/m2, the pH value was 7.4, the electrode gap was 1cm, and when the time was 20min the COD removal efficiency reached 92.8%.The oil removal efficiency of the conventional coagulation was low even with more coagulant agents, and the effluents should be further treated by other methods. In contrast, the coagulation-electrofiotation needs less coagulant agents, resulting in higher removal efficiency. Moreover, the flocs floated to the bulk surface were more compact and easy to be treated.The key factors affecting the oil removal efficiency during the electrocoagulation process are as follows: electroflotation time>current density>pH value>electrodes gap. The optimum operating condition was as follows: the current density was 15.6A/m2, the pH value was 7.4, the electrode gap was 0.5cm, and when the time was 30min the COD removal efficiency reached95%. The aluminum electrodes performed well in the solution with wide range of pH value, and the removal efficiency was higher in the acidic solution than in the alkaline one.COD removal efficiency of practical wastewater from bearing factory is lower treated by electrocoagulation than that by coagulation-electroflotation, but the former did not require additional agents. The oil removal efficiency reached 91% with monopolar electrodes, 94% with bipolar electrodes. The monopolar electrodes configuration is simple and can prevent the occurrence of short circuit.The experimental results show that electrocoagulation and coagulation-electroflotation are suitable for the treatment of the oily emulsion wastewater, with the advantages of compact apparatus, flexible operation and good adaptation.