抗生素类污染物对活性污泥生物毒性测定方法的筛选与评价

尽管衡量化学物质生物毒性的标准方法很多,但关于环境中抗生素类污染物的生物毒性及其对污泥活性影响的科学数据较少。以磺胺和四环素两类作用机理和作用谱带不同的抗生素为研究对象,分别用发光细菌法、脱氢酶活性法、生长抑制法及呼吸速率法进行了抗生素类污染物生物毒性测定方法的筛选与评价。结果表明,发光细菌标准方法中30min的作用时间太短,延长作用时间不仅导致各种抗生素的EC50值大幅度降低,同时毒性排列顺序也发生了改变;以活性污泥为对象的脱氢酶活性和呼吸速率抑制实验的EC50值与抗生素类物质对敏感致病菌的MICs相比异常高,不适宜于作为单独方法准确评估抗生素类污染物的生物毒性。生长抑制实验中,活性污泥混合菌种增殖生长对磺胺类抗生素敏感,而假单胞杆菌对四环素类抗生素敏感。不同方法测定抗生素毒性的灵敏度顺序是发光细菌(24 h)>生长抑制(7 h)>呼吸速率(24 h)>脱氢酶活性(24 h)。用标准方法评价抗生素类污染物的生物毒性,可能导致对抗生素排放到水环境中所带来的风险估计不足。

Screening and evaluation on bioassays of antibiotic pollutants toxicity on activated sludge

Data about the toxicity of antibiotics in the environment and their effects on activity of sewage sludge were very poor, although there were many standard toxicity methods. Sulfonamides and tetracycline with different action mechanism and spectrum were studied, and screening and evaluation on four bioassays including luminescent bacteria test, dehydrogenase activity test, respiration rate test and growth inhibition test were also conducted. The results indicated that 30 min was too short to assess the toxicity of antibiotics, and longer duration of action not only led to significant decrease of EC₅₀ value of each antibiotic, but also great change of the order of toxicity. The EC₅₀-concentrations reported here for the dehydrogenase activity and respiration inhibition test were much higher in the extended medium term test over 24 h than MICs published for sensitive pathogenic bacteria. It was not appropriate for both as separate methods to accurately assess the toxicity of antibiotic pollutants. In the growth inhibition test, complex bacterial populations of activated sludge were sensitive to sulfonamides, while Pseudomonas putida was sensitive to tetracycline. The sensitivity of different methods was luminescent bacteria test (24 h)>growth inhibition test (7 h)>respiration inhibition test (24 h)>dehydrogenase activity (24 h). Toxicity of antibiotics assessed by standard methods might lead to underestimation of the risk of antibiotic in the environment.