Study On Treatment Of Coking Wastewater By Immobilized-Membrane Bioreactor

The coking wastewater was abundant in hydroxybenzene and diffcult to dispose,and contained wide range of contaminants.So Using the traditional biological treatment or any single wastewater treatment technology was difficult to make the coking wastewater COD and NH₄⁺-N meet the discharge standards simultaneously.Membrane Bioreactor(MBR)was a newly developed process which was widely used in the field of water treatment,this method combined membrane separation technology with conventional activated sludge,also had the advantage of increasing organics degradation rate and improving the effluent quality.However,membrane fouling was a perdurable impediment so far during the application of MBR.In this study,Immobilized technology was introduced into MBR system to develop Immobilized-membrane bioreactor with the purpose of controlling membrane fouling.The treatment effect and membrane fouling was compared between Immobilized-MBR and Activated sludge-MBR.The kinetic model of degradation of organic substrates in Immobilized-MBR was established to analyze the parameters.Based on these investigations,the results were shown as following.1.Immobilized-MBR showed good removal efficiency and stability in long-term running,the degradation of COD and NH₄⁺-N was 98.7,95.03 percent respectively.The effluent quality is up to the state's first class standard of discharge water(GB8978-96).2.The treatment results were affected by the volumetric load,HRT,pH,DO. The variations of volumetric load could not affect the results deeply.The anaerobic time was 14 hours and the aerobic time was 10 hours because of the results.The value of pH of the system influenced the effects temporarily,as the result of the experimentation pH was from 7.5 to 8.5.It needed a large DO(＞2 mg/L)in the course in order to dispose NH₄⁺-N.When aerobic time was 8 hours, aeration volume should be reduced.3.After 30 days running,the membrane flux was reduced 20%in Immobilized-membrane bioreactor.Moreover,It is clear that Immobilized technology might be a proper way to reduce the membrane fouling,the membrane permeability could be regained simply by washing the membrane with water.4.The result of Immobilized-MBR showed the better COD degradation rate of 98.7%than Activated sludge-MBR of 93.5%.In addition,the decrease rate of flux of Immobilized-MBR was less than that of Activated sludge-MBR.The flux of IMBR decreased from initial valus of 4.2 L·m^-2·h^-1to the balance value of 3.44 L·m^-2·h^-1,nevertheless,the Activated sludge-MBR was from 4.2 L·m^-2·h^-1to 2.7 L·m^-2·h^-1.5.The kinetic model of degradation of organic substrates in Immobilized-MBR followed zero-order model during the initial water-inputting process,and k₁ equal to 18.49mg·L^-1·h^-1.After then,the kinetic equation of reaction process could be described by one-order model,the parameter of k₃ equal to 0.079h^-1.The analyzing of diffusion process expressed that:when the Thiele modulusφ＜＜1,the entire process rate was controlled by bio-reaction,and whenφ＞＞1,the process was controlled by diffusion.