| Membrane bioreactor (MBR) is a new technology combining membrane separation and biological wastewater treatment, received widely attention. Strengthening the treatment effect and controlling of membrane fouling of membrane bioreactor is research priorities currently. In this study, iron plates were put on both sides of the traditional submerged membrane bioreactor (SMBR) as the sacrificial anode plate of electro-coagulation, building submerged electro-coagulation membrane bioreactor (SECMBR). This study regarded simulated dyeing wastewater and domestic sewage as the research objects, aiming to investigate the microbial properties and pollutant removal in the period of acclimation and operation by SECMBR. The study will provide theoretical and technical support for the application of this treatment process.Firstly, in conditions of 20℃ and aeration of 0.16～0.4m3/h, simulated active black KN-B dyeing wastewater was respectively treated by conventional membrane bioreactor and electro-coagulation membrane bioreactor. In the process, the concentration of reactive dye was gradually increasing from Omg/L to 30mg/L. By measuring the parameters of the activated sludge and water quality, system operation and maintenance conditions, it could be drawn that electro-coagulation membrane bioreactor is superior to conventional membrane bioreactor in terms of efficiency, with resistance to shock loading system and better tolerance of microbial.When the concentration of dye was low(≤15mg/L), activated sludge within two reactors had better adaptability of dyeing wastewater and concentration of sludge rose. When the concentration of dye influent increased, its toxic effects on the microorganisms enhanced, resulting in the significantly decrease of sludge activity within conventional membrane bioreactor and almost no bleaching effect. At the same time, by scanning electron microscopy (SEM) analysis, the number of zoogloea reduced with looser and smaller flocs. However, unit of electro-coagulation in another bioreactor increased the microbial fiocculation of activated sludge and resistance to toxicity, maintaining activity and dye removal capacity in a certain period of time. According to the denaturing gradient gel electrophoresis (DGGE) patterns of different stages of dye concentration in two reactors, electro-coagulation membrane bioreactor had generated dominant species with adaptive of reactive black dye wastewater, so the system had a certain ability of decolorization.Secondly, taking electro-coagulation membrane bioreactor as the core technology, and parallel operating traditional membrane bioreactor and electric membrane bioreactor, study COD and ammonia nitrogen removal efficiency with different process parameters of the two systems. In the hydraulic retention time (HRT) of 4h, 6h and 8h variable experiments, with the increase of HRT, efficiency of COD within electro-coagulation MBR were 62.34%,71.40% and 75.68%. Respectively, ammonia removal efficiency were 62.07%,63.97% and 91.76%. It could be drawn that the increase of HRT could improve the processing efficiency. Meanwhile, through the comparison of efficiency, it was better in stability than the conventional membrane bioreactor. Aeration (0.2m3/h,0.4m3/h and 0.6m3/h) variable experiments showed that aeration of 0.6m3/h affected the adsorption and degradation of organic matters, resulting in fluctuation of COD removal rate and instability of system. While for ammonia removal, along with the increase of aeration, activity of nitrifying and denitrifying bacteria in the electro-coagulation membrane bioreactor increased and ammonia removal efficiency had significantly improved up to 98% than that in 0.2m3/h. In the conditions of current densities of 0.083mA/cm2,0.183mA/cm2 and 0.43mA/cm2, the efficiency had enhanced with the increase of current density. When it was under 0.083mA/cm2, the system was easier to have normal operating conditions with slow increase of COD removal rate. At the same time, ammonia nitrogen removal efficiency had improved by 10% than that in the conventional MBR system. And with the increase of current density, the advantages of the system diminished.Through discussion and analysis, the optimum experimental parameters of electro-coagulation membrane bioreactor for domestic wastewater treatment were: HRT=8h; aeration capacity of 0.4m3/h; current density of 0.083mA/cm2. Under this circumstance, the system could get about 75.68% of COD removal rate and 98.95% of ammonia removal rate. In term of the removal of phosphorus, electro-coagulation membrane bioreactor had strong ability of phosphorus absorption, compared with the other two bioreactor. The concentration of phosphorus of the effluent decreased by about 56.82% than that of the other two effluents. These obvious advantages attributed to the unit effect of electro-coagulation.Wastewater treatment by these methods had shown that:(1) compared to the conventional membrane bioreactor, electro-coagulation membrane bioreactor can increase the tolerance of sludge; (2)for domestic sewage treatment, electro-coagulation MBR had a high removal efficiency of ammonia nitrogen. Ammonia concentration of effluent could reach standard B of emission standard GB18918-2002; (3) the system had strong anti-shock loading ability and good stability, which can actually provide a new reference for the treatment of wastewater. |
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