Study On The Characteristics And Mechanism Of Degradation Of Ciprofloxacin By Biological Sponge Iron System

Ciprofloxacin?CIP?is a synthetic antibiotic with good antibacterial activity and strong toxicity to microorganisms.Because it is widely used in medical,aquaculture and other industries,it contains a certain amount of CIP in the influent of municipal sewage treatment plants,and its concentration reaches ng·L^-1 or even mg·L^-1 level,which is the normal biochemical treatment of urban sewage treatment plants.It has a certain impact and even causes serious damage to the aquatic environment.Therefore,it is particularly important to develop a CIP process that is economical and easy to use for engineering applications.The biological sponge iron system is a complex system formed by injecting sponge iron into activated sludge in a certain way.The system has many complicated functions such as iron-carbon micro-electrolysis,bio-iron method,Fe⁰/O₂ system,etc.It is indicated that Fe²⁺eluted by electrophoresis and biological action of sponge iron can produce H₂O₂ and·OH while oxidizing,which promotes the generation of Fenton reaction in the system and strengthens degradation of refractory organic matter,but the research on CIP is rarely reported.In this study,the simulated CIP wastewater was used as the object.The strong oxidation of ciprofloxacin by biological sponge iron system was investigated by parallel contrast experiments.The effect of reactor operating conditions on the degradation of CIP in biological sponge iron system and its degradation mechanism were discussed.A preliminary discussion was conducted.In addition,a high-efficiency CIP-degrading strain with iron oxidation function was screened from a long-running bio-sprayed iron reactor degrading ciprofloxacin.The growth and degradation characteristics of the strain in CIP wastewater were investigated.The study draws the following conclusions:?1?Regardless of the degradation effect of COD and CIP,or the adaptability and impact resistance of high concentration CIP,the biological sponge iron system is better than the sponge iron system and the common activated sludge system,when the CIP concentration is increased to 5 mg.When the ordinary activated sludge system has completely disintegrated,and the reaction system has completely lost the ability to degrade CIP.?2?The biological sponge iron system has good tolerance and degradation rate under the CIP concentration of 20mg/L.The optimal sponge iron particle size is 300 mesh iron powder,and the optimal dosage of sponge iron is 45g/L.The optimum initial pH was 5,verifying that the Fenton-like effect generally occurs in an acidic environment.?3?A strain of CIP high-efficiency bacteria with iron oxidation function was screened and named as strain P-3,which is a Gram-negative bacteria.The growth curve of the strain was fitted by Logistic equation,and the growth amount of the strain reached the maximum at 16h.The optimal reaction conditions for the degradation of CIP by the strain were as follows:the bacterial liquid dosage was 10%,the temperature was 30°C,and the pH was 7.?4?Using GC-MS to monitor the change of CIP and the concentration of intermediate product in the period of batch biological sponge iron system,it was found that CIP degradation products include small molecules such as malonic acid,urea,propylene glycol and terephthalic acid.The effect of bio-sponge iron system on the degradation of CIP was analyzed by parallel comparison experiments of domesticated activated sludge system,inactivated domesticated activated sludge system and inactivated acclimated activated sludge system+quencher.It was found that the proportion of degradation of the system was 71.48%for adsorption,17.23%for biological action,and 11.31%for Fenton,and other effects were neglected.