Biodegradation And Removal Kinetics Of Fluoroquinolone Antibiotics In Sludge Composting

Fluoroquinolones?FQs?are widely used in the prevention and treatment of human and livestock diseases.Because they are not easily metabolized by organisms,which being usually excreted as prototypes and being often detected in the environment including water,soil and so on.60%⁷0%of the FQs in the sewage are adsorbed and enter into the sludge,which has potential environmental risks for the resource-based land utilization after composting.In this study,norfloxacin?NOR?and ofloxacin?OFL?were chosen as research objects to study the biodegradation mechanism of FQs in the aerobic composting and the influence of environmental factors on its removal efficiency.Which would provide basic data on the environment risk assessment of FQs,and provide basis to optimize the process of FQs residue degraded in municipal sludge.Firstly,the biodegradation mechanism of NOR and OFL were researched.The materials were taken out of three stages including temperature raising period,high temperature period and maturing period.Adding the amount of FQs into which to 5mg/kg,the biodegradation experiment were carried out through adjusting the 70%moisture and controlling the corresponding temperature through water bath pot heating,at the same time,keeping ventilating into the materials.The high temperature sterilized materials were as controls.The activities of different kinds of biodegradation enzymes were different in different composting stages.The activity of Lac was the biggest in medium temperature,but not being detected in the high temperature.The certain activities of MnP and LiP existed in different materials.The results indicated that the main metabolic pathways of NOR in 0⁷ d was similar with that in medium temperature,in high temperature and in maturity materials.There were two degradation pathways in medium temperature and in high temperature materials including that C₂H₂ of NOR being removed,then acetylating,and losing C₄H₇NO.The other pathway was that NOR acetylating,then removing C₂H₂,and finally losing C₄H₇NO.The main metabolic pathway of NOR in decomposed materials was consistent with that in the second metabolic pathway in medium-temperature and in high-temperature materials.The main metabolic pathways in the first 7 days of OFL in medium temperature and in high temperature materials were OFL demethylating,then acetylating,and removing C₂H₂,finally removing C₄H₇NO.There were two metabolic pathways in the decomposed materials,including that OFL losing C₂H₂ and C₃H₇N.Which of another pathway demethylating,formylating,and removing C₂H₂ and C₃H₅NO.In addition,the study researched the self-time change of FQs through controlling three kinds of additive amount of which including 0,2.5 and 5 mg/kg.The results demonstrated that the bigger the initial concentrations of FQs,the bigger the self-time of FQs.The self-time of FQs was between 35.6 days and 69.3 days,which not being added in the materials,which was between 63.6 days and 123.8 days when the amount of FQs being added up to 5 mg/kg in the materials.Under the condition of different material moisture content,the self-time of FQs reduced in medium temperature materials sorting by 60%>50%>70%of the moisture content.The self-time of NOR and OFL was the smallest in the 60%moisture content,which was 68.6 days and 83.5days respectively.The self-time of NOR and OFL reduced in medium temperature materials sorting by 50%>60%>70%of the moisture content.The self-time of NOR and OFL was the smallest in the 70%moisture content,which was 68.6 days and 83.5days respectively.In addition,the self-time of FQs was smaller under the aerobic conditions than that under the anaerobic conditions.The self-time of FQs was between68.6 days and 123.8 days under the aerobic conditions.However,which was between157.5 days and 239.0 days under the anaerobic conditions.