| Tetracycline is one kind of topicial broad-spectrum antibiotics, which is concerned about its distribution fate and resistance in all kinds of environment for years. Aerobiotic activated sludge is the most widely used biological treatment process in wastewater treatment system. In this article, the impact of tetracycline to aerobiotic activated sludge was discussed, in order to realize the role of tetracycline to tetracycline resistance in wastewater treatment process. And the conclusion is supposed to provide fundamental basis for the elimination of tetracycline and tetracycline resistance in wastewater treatment system.Complicated interactions were found in this article, the main conclusions were listed below:①Tetracycline is adsorptive to aerobiotic activated sludge.Adsorption of tetracycline to activated sludge was accored with pseudo secondary adsorption kinetics modle. The higher tetracycline concentration and the smaller MLSS, the longer adsorption equilibrium time is. When the MLSS was settled, adsorption quantity increased with the increace of tetracycline concentration; when the tetracycline was settled, adsorption quantity decreased with the increase of MLSS, and the adsorption rate was just the reverse.The adsorption of tetracycline on aerobiotic activated sludge was fitted to different adsorption model. Under indoor temperature, the adsorption showed abundant forms, and was accored with Langmuir, Freundlich and Henry model. It was an endothermic rection, and with the rise of temperature, the adsorption capacity was enhanced.The adsorption of tetracycline on aerobiotic activated sludge was influenced by pH, ion strength and other factor. When pH was6, the adsorption quantity was max, and the adsorption quantity reduced with the pH increased. The positive ion inhibited the adsorption. There were two adsorption mechanisms in the adsorption of tetracycline on aerobiotic activated sludge:ion exchange and electrostatic adsorption. ②It is not easy for tetracycline to desorb from the aerobiotic activated sludge.The desorb rate was only2.16%when use deionize water as desorption reagent. ENTA-Na2showed the best desorb capability, after by CaCl2, AICl3and citric acid, while NaCl showed the similar capability with deionize water.③Tetracycline inhibited aerobiotic activated sludge badly.Tetraycline showed obviouse inhibition to the dehydrogenase of aerobiotic activated sludge. When the tetracycline concentration was above20mg-L"1, the inhibition rate of tetracycline to dehydrogenase was up to80%. The inhibition of tetracycline to dehydrogenase was fitted to Logistic equation, and the EC50was11.72mg·L-1.Tetracycline also inhibited the COD removal capability of aerobiotic activated sludge. With the increace of tetracycline concentration, inhibition showed obviously. The high MLSS cushioned the inhibition from tetracycline, but the cushion did not play a part when the tetracycline concentration was above10mg-L-1.Tetracycline inhibited sludge growth yield of aerobiotic activated sludge seriously. When the tetracycline concentration was above20mg-L-1, both the test sludge got a zero sludge growth yield.④Tetracycline selected the tetracycline resistance in aerobiotic activated sludge.Both tetracycline intermediate resistant and tetracycline resistant heterotrophic bacteria in total heterotrophic bacteria were significantly increased under the tetracycline concentration of500μg·L-1, and two kinds of tet genes(tet A and tet B) was accumulated. Different operation patterns influence the tetracycline resistance, slower and continuous influent and shorter hydraulic retention time could make the increase of tetracycline resistance increace easier.It was proposed in this study that tetracycline resistant genes created by efflux pumps spread earlier and quicker to encode resistance to tetracycline, which facilitated the increase in tetracycline resistance. |
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