Experimental Research On Treatment Of High Concentration Textile Wastewater By Pulsed Electro-coagulation

Textile wastewater has been one of the most difficult problems for prevention ofwater pollution. Single treating method for textile wastewater can not make the quality oftreated wastewater to meet the wastewater discharge standards. Therefore, combinedphysicochemical and biological process is often used for textile wastewater treatment. Theprimary treatment holds the important status in the entire process, which will affect thebiochemical process effect directly. Compared with the conventional electro-coagulation,pulsed electro-coagulation technology has the advantage of lower energy consumptionand apply the pulse power electrolysis can eliminate the behavior of anode passivation inthe process of electro-coagulation. According to the character of textile wastewater from atextile plant, the pulsed electro-coagulation is chosen to do the experiment. Key factorsaffecting on the treatment effect of pulsed electro-coagulation including electrode material,electrolytic time, applied voltage and initial pH of textile wastewater are investigated.UV-vis spectra and three dimensional fluorescence spectrum are used to analyze thecomposition of textile wastewater before and after treatment. During the processing oftreatment, hydroxyl radical is detected and analyzed in order to explore the mechanism oftextile wastewater treatment by pulsed electro-coagulation. In this paper, the mainresearch contents and conclusions are as follows:(1) The optimum operation conditions of this equipment are determined by factorexperiments. In consideration of treatment effect and energy consumption, the optimumoperation condition of the equipment are as follows: iron is used as the electrode material;reaction time is15min; voltage is120V; the initial pH is about6. When treating thetextile wastewater that the concentration of COD is5328mg·L-1; NH4+-N is595mg·L-1and the chrome is400, the removal rates of COD、NH4+-N and chrome can reach79.45%、23.89%and87.50%respectively under the optimal operating condition. The energyconsumption of a small pilot plant operation is about2.82~3.81kWh/kgCOD.(2) UV-visible spectra show that the absorption peak appears at a wavelength near220nm and280nm, indicating that the wastewater may contain benzene ring, benzenecarboxylic acids base, benzene hydroxyl and other substances. For three different platematerials such as iron plate, aluminum plate and stainless steel plate, the results show thatthe decrease of absorbance value is the sharpest when use iron electrode, indicating that using iron plate electrodes to treat textile wastewater can reach the best effect, and this isconsistent with the experiment results. The derivative spectroscopy shows that thematerial composition and concentration in the water after treatment by pulsedelectro-coagulation must be changed.(3) Three-dimensional (3D) excitation-emission matrix (EEM) fluorescencespectroscopy is applied to characterize the wastewater before and after treatment. Theresults show that the main composition of the influent is fulvic-like and humic-like acid.After treatment, the fluorescent area not changed obviously, but very significant change influorescence intensity. This indicates that the type and quantity of waste material haschanged.(4) Using dimethyl sulfoxide (DMSO)-spectrophotometric method to determine thecontent of hydroxyl radicals during the wastewater treatment process, the results showthat a certain amount of hydroxyl radicals are generated in reaction system, and thequantity of hydroxyl radicals is different by using different electrode materials.(5) Studies indicate that the main reaction of this apparatus is still theelectrochemical flocculation and electrochemical flotation and the electrochemicaloxidation is weak.(6) The medium-scale experiment is conducted by using pulsed electro-coagulationequipment with the processing capacity of0.5m3/h. It is obvious that pulsedelectro-coagulation technology has advantages in pollutant removal efficiency, energyconsumption, floor coverage and chemical additive. And on the basis of enlargement ofmedium-scale experiment, the pulsed electro-coagulation technology can be used toreplace the original pretreatment process.