Parabens are preservatives widely used in foodstuffs, cosmetics and pharmaceuticals, which have led to elevated paraben concentrations in wastewater and receiving waters. Laboratory-scale batch experiments were conducted to investigate the adsorption and degradation of parabens in an aerobic activated sludge system. Results show that biodegradation plays a key role in removing parabens from the aerobic system of wastewater treatment plants, while adsorption on the sludge is not significant. The effects of parent paraben concentration, concentration of mixed liquor suspended solids (MLSS), initial pH and temperature on degradation were investigated using kinetic models. The data shows that the degradation of parabens could be described by the first-order kinetic model with the rate constant ranging from 0.10 to 0.88 h⁻¹ at 25 °C and pH 7.0. Paraben degradation can be enhanced by increasing the MLSS concentration and temperature, or by decreasing the parent paraben concentration. Furthermore, the pH of the incubation system should be lower than 8.0. The half-lives of the parabens were estimated to range between 0.79 and 6.9 h, with methylparaben exhibiting the slowest degradation rate. During degradation in the present system, transesterification occurred, with methylparaben being the major transformation product in the incubation systems of ethylparaben, propylparaben and butylparaben. These results were confirmed by mass spectrometry and aliphatic alcohol additive experiments. This is the first discovery of paraben transesterification in an activated sludge system, and it is associated with trace methanol in the system.

对羟基苯甲酸酯是广泛用于食品，化妆品和药品中的防腐剂，已导致废水和接收水中的对羟基苯甲酸酯浓度升高。进行了实验室规模的分批实验，以研究好氧活性污泥系统中对羟基苯甲酸酯的吸附和降解。结果表明，生物降解在去除废水处理厂好氧系统中的对羟基苯甲酸酯方面起着关键作用，而污泥上的吸附作用并不显着。使用动力学模型研究了母体对羟基苯甲酸酯浓度，混合液悬浮固体浓度（MLSS），初始pH和温度对降解的影响。数据表明，对羟基苯甲酸酯的降解可以用一阶动力学模型描述，速率常数范围为0.10至0.88 h ^-1在25°C和pH 7.0下。可以通过增加MLSS浓度和温度或降低母体对羟基苯甲酸酯浓度来增强对羟基苯甲酸酯的降解。此外，温育系统的pH值应低于8.0。对羟基苯甲酸酯的半衰期估计在0.79至6.9小时之间，对羟基苯甲酸甲酯的降解速度最慢。在本系统的降解过程中，发生了酯交换反应，对羟基苯甲酸甲酯是对羟基苯甲酸乙酯，对羟基苯甲酸丙酯和对羟基苯甲酸丁酯孵育系统中的主要转化产物。这些结果通过质谱和脂肪族醇添加剂实验得到了证实。这是活性污泥系统中对羟基苯甲酸酯基酯交换的第一个发现，并且与系统中的痕量甲醇有关。