A/O系统处理低C/N奶牛场废水中的抗生素

Treatment of antibiotics in low C/N ratio dairy farm wastewater by anoxicoxic system

为处理奶牛场废水中常检出抗生素,考察了小试规模缺氧/好氧(A/O)系统对低C/N奶牛场废水中常规污染物和抗生素的处理效果。当进水COD、总氮、氨氮和总磷分别在1 242~4 350、830~1 367、818~1 291和6~12 mg·L^-1, A池和O池水力停留时间(HRT)分别为3~4 d和2.05~5.4 d时,系统出水COD<400 mg·L^-1、氨氮<10 mg·L^-1、总氮去除率为40%~60%(无外加碳源)、总磷基本没有去除;通过调节硝化液回流比(1.0∶1~1.3∶1)可在进水COD/总氮≥3.1时实现碱度的自给自足;对11种磺胺类和8种β-内酰胺类抗生素研究发现,共检出9种磺胺类和1种β-内酰胺类抗生素(总浓度为5.89~17.31μg·L^-1),系统对抗生素的总去除率大于93%;先后2次向进水中人为添加8种磺胺类抗生素(每种浓度先后为50μg·L^-1和200μg·L^-1)不会影响系统运行的稳定性,且抗生素的总去除率大于90%,A池和O池的抗生素去除率分别为15.0%~34.2%和69.1%~91.4%;在O池中的HRT降低50%时,系统对抗生素的总去除率基本不变。除甲氧苄啶外,其余7种磺胺类抗生素主要在O池中均得到去除,这与其分子结构中的S—N键有关。以上结果对奶牛场废水处理后还田具有重要的参考价值。

Antibiotics are often detected in dairy farm wastewater. The treatment effects of conventional pollutants and antibiotics in low C/N ratio dairy farm wastewater were investigated by using a bench-scale anoxic-oxic(A/O) system. When the COD, total nitrogen(TN), ammonia nitrogen and total phosphorus(TP) in the influent were 1 242~4 350, 830~1 367, 818~1 291 and 6~12 mg·L^-1, respectively, and the hydraulic retention times(HRTs) of anoxic and oxic reactor were 3~4 and 2.1~5.4 d, respectively, COD and ammonia nitrogen in the effluent of the system were less than 400 mg·L^-1 and 10 mg·L^-1, respectively, TN removal rate was 40%~60%(without additional carbon source), and TP was almost not removed. By adjusting the recycle ratio of nitrified liquor(1.0∶1~1.3∶1), the self-sufficiency of alkalinity could be realized when the COD/TN ratio of influent water was not less than 3.1. Based on the analysis of 11 kinds of sulfonamide and 8 kinds of β-lactam antibiotics in the wastewater, 9 sulfonamides and one β-lactam antibiotic were detected in the system(the total concentration was 5.89~17.31 μg·L^-1), and the total removal efficiency of them was more than 93%.Adding 8 kinds of sulfonamide antibiotics to the influent twice(firstly 50 μg·L^-1 for each antibiotics and secondly 200 μg·L^-1 for each antibiotics) did not affect the stability of the system, and the total removal efficiency of antibiotics was more than 90%, and the removal rates of antibiotics in anoxic reactor and oxic reactor were 15.02%~34.23% and 69.1%~91.43%, respectively. Reducing the HRT of oxic reactor to 50% did not affect the antibiotics removal rate by the system. Except trimethoprim, the other 7 kinds of sulfonamide antibiotics were mainly removed in oxic reactor, which was related to the S-N bond in their molecular structures.The above results have important reference value for dairy farm wastewater treatment and returning to farmland.