洛美沙星对水中反硝化过程的影响模拟试验

水环境中硝酸盐的去除依赖于微生物在厌氧条件下进行的反硝化作用，已有研究发现，抗生素的存在会对反硝化细菌和反硝化酶活性产生一定影响，进而影响反硝化作用，但目前在水体中对于这三者之间关系的研究较少，作用的机理尚未完全明确.据此，本文以洛美沙星（Lomefloxacin，LOM）为典型抗生素，乙酸钠为碳源开展模拟实验，对反硝化过程、反硝化细菌和反硝化酶活性的影响进行探讨.实验结果表明，含有0，1，10，100 μg/L LOM的反应体系反硝化速率分别为10.42，8.83，8.50，6.62mg/（L·d），脱氮率分别为79.5%，71.1%，70.0%，66.8%，LOM初始浓度为100μg/L时对反硝化细菌生长的抑制率高达30.5%.推测含有一定浓度LOM会对反硝化细菌的生长发育以及反硝化酶活性产生影响，导致反硝化过程中NO₃^--N的转化受到抑制，进而引起反硝化速率和总氮去除率降低，且LOM初始浓度越大，抑制作用越显著（P<0.05）.进一步分析结果表明，LOM影响反硝化作用主要表现在NO₃^--N还原至NO₂^--N这一过程，LOM初始浓度越高会使细菌生长速率和最大增长量减少，微生物的细胞膜完整性遭破坏程度增大.NO₃^--N和NO₂^--N的转化与反硝化酶活性有关，其中LOM浓度对硝酸盐还原酶活性的影响明显，浓度越大受到抑制程度也越大，但对亚硝酸盐还原酶活性几乎不产生影响.以上模拟试验条件虽距实际条件有所差异，但在一定程度上表明环境水体中低浓度抗生素影响反硝化作用的机理表现为抑制微生物生长和活性以及反硝化酶活性，降低脱氮率，导致硝酸盐污染的积累.

Simulation experiments on effects of lomefloxacin on denitrification process in water

The removal of nitrate in aquatic environment depends on denitrification by microorganisms under anaerobic conditions. It has been found that the presence of antibiotics can affect the activity of denitrifying bacteria and denitrifying enzymes, and then affect denitrification. However, the relationships among these three factors and the potential influencing mechanisms remains unclear in water system. In this study, simulation experiments were carried out to determine the effects of antibiotic on denitrification process, denitrification bacteria and denitrification enzyme activities. In the experiments, lomefloxacin (LOM) was selected as a typical antibiotic and sodium acetate was used as a carbon source. The results showed that the denitrification rates exposed to 0, 1, 10 and 100μg/L LOM were 10.42, 8.83, 8.50 and 6.62mg/(L·d), and the nitrogen removal reached 79.5%, 71.1%, 70.0% and 66.8%, respectively. For 100μg/L LOM exposure, the inhibition rate on denitrifying bacteria was up to 30.5%. This suggested that LOM with a certain concentration could affect the microbial growth processes and denitrifying enzyme activity. Therefore, the inhibition of NO₃^--N transformation during denitrification was observed, which further led to the decrease in denitrification and total nitrogen removal rate. Moreover, the higher the initial LOM concentration, the more significant the inhibition effect (P<0.05). Further results demonstrated that effects of LOM on denitrification mainly functioned in the process of NO₃^--N reduction to NO₂^--N. With increasing initial LOM concentration, the growth rate and maximum increment of bacteria decreased, and the damage to the integrity of microbial cell membrane became worse. The transformation of NO₃^--N and NO₂^--N was related to denitrifying enzyme activity. LOM concentration had a significant influence on nitrate reductase activity. The higher the concentration, the greater the degree of inhibition. However, the activity of nitrite reductase was hardly affected LOM concentration. Although the above simulated experimental conditions did not completely matched with the real water, the results implied that the low concentration of antibiotics in environment water body is likely to affect the denitrification process by inhibiting the microbial population and activity as well as the denitrifying enzyme activity, and consequently reduce the denitrification rate and lead to the accumulation of nitrate pollution.