Study On The Treatment Of Citric Acid Washing Wastewater With A Membrane Bio-Reactor

Membrane bioreactor (MBR) is a wastewater treatment technology, which combined membrane separation technology and biological treatment technology. It has a lot of advantages such as simple process, good effluent, little excess sludge, etal. MBR has been developing and broading its applying fields, and has attracted more and more attention.In this study, it is reviewed that the development and the application of membrane bioreactor, and that study of fouling control for ultra-filtration membrane at home and abroad. The treatment of citric acid wastewater was studied with re-circulated Membrane Bioreactor on the basis of the development tendency and exiting program. In this paper, the feasibility and the treatment effect of using membrane bioreactor to treat citric acid wastewater was studied. Experiments were carried out to investigate the operation controlling condition systematically, optimize the operation condition of membrane bioreactor.The difference hydraulic retain time(HRT) and the volume of air-blow was studied, the transformations and the removal efficiency of various water quality quota was observed and studied. The effect of the treatment of citric acid wastewater during long-term operation had showed: Under the condition of 12h HRT and 4~5mg/L dissolve oxygen, the membrane bioreactor had a good effect on the removal of pollutants. The quality of the effluent had good stability.The evolution of sludge concentrations and growth mechanism was analyzed in this paper. During the course of the operation, sludge appearance has been changed, the color was changed from black to dust color and finally changed ton snuff color, and MLSS(mixed liquor suspended solid) increased from 4.7g/L to 9.3 g/L, and the microorganism status of the membrane bioreactor were estimated by the means that the microbe phase of sludge mixed liquid were observed by microscope.The MBR separation and filtration characteristic was described. The character of fouling UF membrane and the influence of membrane flux were found out. The correlativity between membrane flux and temperature, pressure, MLSS was set up separately. These provided bases to the control of operational conditions in re-circulated MBR.Under the deeply study of the character of fouling UF membrane, an effective membrane cleaning procedure was determined including physical and chemical cleaning methods. And they had a good effect. The time and the period of backwash were determined. The backwash which combined with front wash was superior to the single backwash; moreover, the types of chemical agents and the period of chemical cleaning were decided through chemical cleaning method. They had a good effect.Membrane bioreactor can be used to treat citric acid wastewater, and had a fine effect on the removal of chemical oxygen demand (COD), ammonia nitrogen(NH3 — N), phosphorus(P), ferric(Fe) and solid suspended solid(SS). The removal rate can reach above 90%, The quality of the effluent had good stability.