The Degradation Behavior Of TCH And The Response Of Microorganisms In An Intimate Coupling Of Photocatalysis And Biodegradation Reactor

Tetracycline, as the most widely used antibiotics, make great contribution to the control of disease. However, the inappropriate use and production of antibiotics will lead them to flow into the environment and give rise to the health threat for human beings and other creatures. Therefore, it is necessary for us to propose a suitable solution to treat the tetracycline.There are fatal flaws of the degradation of complex organic pollutants by individual photocatalytic oxidation, biodegradation, as well as sequence photocatalytic and biodegradation, of their respective. However the method of intimate coupling of photocatalytic and biodegradation can overcome their drawbacks above. By this way, the degradation and mineraliazation of refractory organics could be achieved, and the conservation of energy resources could be done to the greatest degree.For this reason, the target pollutant of present study is tetracycline. The method of intimate coupling of photocatalytic and biodegradation will be used to study the degradation and mineralization of tetracycline. By compared with individual photocatalytic oxidation and biodegradation, the degradation condition and the response of the microorganisms will be analyzed.During the study, we found that tetracycline had two absorption peaks in the wavelength of 275 nm and 357 nm when the solution of tetracycline was scanned by UV-visible spectrophotometer. The results show that both the efficiency of the individual photocatalytic oxidation and intimate coupling of photocatalytic and biodegradation can reach to 90% in the wavelength of 357 nm. However the result of 275 nm shows different condition. In the reaction of photocatalysis, the degradation efficiency in 12 h is still up to 90%. But when it comes to the reaction of intimate coupling of photocatalytic and biodegradation, the reaction in this system makes a first increased and then decreased tendency. This result proves that, in the reaction of intimate coupling of photocatalytic and biodegradation, there are some intermediates generated, accumulated and degraded whose molecular structures is similar to aromatic ring A or whose absorption peaks is close to the wavelength of 275 nm. According to the difference of the two results, it can be inferred that the reaction of intimate coupling of photocatalytic and biodegradation can promote the degradation of TCH toward a certain direction which can facilitate the decomposition of TCH to some intermediates that are much more easier to biodegradation.The result of BOD₅ shows that the reaction of intimate coupling of photocatalytic and biodegradation can improve the biodegradability of the solution effectively, which proves that it is more conductive for this system to maintain the survival of the microorganisms. Meanwhile, the microorganisms in the carriers can be protected in the system of intimate coupling of photocatalytic and biodegradation. Furthermore, in this system, the microbial activity、normal physiological activity and secretory activity of microorganisms can be maintained and even promoted. When compared to the change of biological community structure in both biodegradation and intimate coupling of photocatalytic and biodegradation, the results of intimate coupling of photocatalytic and biodegradation show some changes that can not be ignored. The bacteria which can assimilate naphthalene ring and phenols as their carbon source exist in this system and show a competitive advantage. The results above prove that the rings in the TCH can be opened and some intermediates which are more readily biodegraded can be generated. Therefore, some kind of bacteria which can assimilate them have an advantage to grow and can promote the decomposition of TCH and its intermediates constantly.In this study, a new system called intimate coupling of photocatalytic and biodegradation is used to degrade TCH, and then the behavior of degradation and the response of the microorganisms in this system are analyzed. The results indicates that the system we used shows a greater ability in degrading the TCH, compared to single process. This study can provide a theoretical basis and practical experience for the development of the intimate coupling of photocatalytic and biodegradation and the treatment of antibiotic wastewater.