Study On The Relationship Between Biofilms On The Ceramic Carriers And Wastewater Treatment

With the rapid development of industrial and agricultural production, many lakes, reservoir and urban river pose a severe risk of eutrophication caused by excessive nitrogen levels, which led to cyanobacteria bloom frequently. Thus the environmental problem caused by the nitrogen contamination has aroused people's attention increasingly. Aiming at water pollution caused by excessive nitrogen levels, various kinds of biological methods are carried for treatment, among which biofilm technology is an effective method. It is necessary for us to learn regularity of biofilm in order to improve the technology of wastewater treatment, although it is a complex system between biofilm's structure and wastewater treatment, and lack of studies on biofilm concerned.Situation of biofilm on the ceramic carriers and some effect factors were discussed in this article in three parts.Part one: Microelectrode was used to measure oxygen concentration inside the biofilm under different growth stages, and then investigate biofilm's growth procedure as well as its bioactivity. With the increasing of biofilm thickness, biofilm's micro-structure loosed from densification to be resulted in that DO permeation rate change. Based on the data, diffusion reaction equation was established, which was identical to zero order kinetic equation.Part two: Regularities of organic compound degradation were discussed under different conditions with biofilm's inner-structure variation. It was discussed mainly that the inner structure of biofilm was affected by different position in the reactor, different substrate flow velocities, and different carbon recourses. Biofilm had complex formation, either dense or loose in reactor, in the lower flowing velocity or relatively longer HRT, or lower load condition. Distinct micro-structure is cultured by different carbon sources, which affect the bacteria species growth and microbial distribution and lead to different bioactivity, and oxygen transfer efficiency, which vary the wastewater treatment effect.Part three: Biofilm was used in treatment of electroplating wastewater, in which glucose and methanol as carbon source were respectively fed into the wastewater to promote biofilm grow. The biofilm was porosity corresponding to glucose and oxygen concentration was about 4.7mg/L at the depth of 1mm under the biofilm. While the biofilm was dense when methanol was used as carbon source, oxygen concentration tended to zero at the depth of 0.5mm under the bioflim surface. A porous biofilm was suit for mass to transport, which resulted in higher ammonia nitrogen removal percentage, otherwise dense biofilm was hard for ammonia nitrogen to be removed.Biofilm's structure could be characterized by dissolve oxygen concentration insider it. Microelectrode was used for monitoring biofilm to investigat the micro-reactive kinetics occurred in biofilm. The results indicated that neither too dense nor too loosen biofilm was the best one, while external loosen and internal dense biofilm made more reasonable bacteria distribution, which would achieved better effect of wastewater treatment.