| Ciprofloxacin(CIP)is a broad-spectrum antibacterial drug and widely used in China and abroad in recent years.Large amounts of poisonous organic wastewater with high concentrations of organic compounds such as antibiotics and pharmaceutical intermediates are produced during the course of CIP production,which have strong antibacterial activity and are difficult to biodegrade directly,thus it may do great harm to environmental health once discharged into natural waters.Therefore,it is very urgent and necessary to develop an efficient treatment technology of ciprofloxacin wastewater.In this study,novel Fe-C ceramsite and light sludge ceramic media were separately used in Fe-C micro-electrolysis pretreatment system and series up-flow anaerobic-aerobic biological filter(UAF-UBAF)system to treat the synthetic CIP wastewater.The study preliminarily proved the feasibility and superiority of the combined Fe-C micro-electrolysis and UAF-UBAF system in treating CIP wastewater by conducting a series of experimental studies.In the meanwhile,the suitable operating conditions of the combined process were determined to provide theoretical basis and practical guidance for the design and application of practical engineering.The effects of influent pH,gas water ratio(A/L)and hydraulic residence time(HRT)on CODcr,TOC and CIP removal were investigated in the pretreatment study of Fe-C micro-electrolysis based on novel Fe-C ceramsite for CIP wastewater treatment.The optimum operating condations of Fe-C micro-electrolysis were:influent pH of 4.0,A/L of 15 and HRT of 3 h.Under the optimal conditions,the removal rates of CODcr,TOC and CIP were stable at 57%,73%and 34%respectively.The results showed that a significant increase from 0.21 to 0.43 of BOD5/COD ratio was achieved,which implied that the contaminants in wastewater had become more prone to biodegradation.On the basis of the optimized Fe-C micro-electrolysis system,a combined system of Fe-C micro-electrolysis and UABF based on novel ceramic media was established in the study to treat CIP wastewater.The removal rates of CODcr,NH4-N,TP and CIP were investigated.The results showed that the removal rates of CODcr,NH4-N,TP and CIP respectively reached to 90%,95%,98%and 97%when the concentration of CODcr and CIP were 1000 mg/L and 50-70 mg/L.As a result,the Fe-C micro-electrolysis and UABF combined system can achieve the aim of simultaneously removing carbon,phosphorus and ciprofloxacin under the load of low organic load and high ciprofloxacin.In the combined process,the pretreatment of Fe-C micro-electrolysis greatly promoted the removal of TP and CIP.In the study,the effect of CIP on the structure succession of aerobic microorganism in UBAF was further studied and the degradation mechanism of CIP in the combined Fe-C micro-electrolysis and UABF system was analyzed.The high-throughput sequencing analysis showed that the microbial community changed a lot under CIP pressure.The richness,evenness and diversity of the microbial community increased simultaneously with CIP pressure.According to the changes of microorganism population and the function of bacteria,the microbial species of CIP biodegradation in UBAF mainly include:Sphingomonadaceae,Comamonadaceae,Ralstonia,Bradyrhizobium,Xanthomonadaceae,Rhizobiaceae,Helicobacter and Pseudomonas,etc.Four main degradation pathways were proposed according to the LC-MS analysis.More than 12 degradation products were detected through the treatment of Fe-C micro electrolysis and only 3 biodegraded products with low concentration were identified in BAF effluent.In order to effectively treat the CIP wastewater containing high concentration of organic matter and CIP,the novel combined system of Fe-C micro electrolysis and UAF-UBAF was further established.The effect of influent organic load and CIP load on the operation of composite system was investigated.The results showed that the removal rates of CODcr,NH4-N,TP and CIP respectively reached to 98%,96%,90%and 98%when the concentration of CODcr and CIP were 3000 mg/L and 100 mg/L.In continuous running mode,the Fe-C micro electrolysis and UAF-UBAF system showed high organic load and strong resistance to impact load during the treatment of CIP wastewater.In addition,a strong ability of tolerating and degrading CIP was observed in the combined system.Finally,in this study,the strengthening methods of the Fe-C micro-electrolysis based on Fe-C ceramsite were studied,including the strengthening effects of forming catalytic micro-electrolysis system and applying additonal dc power.First of all,the novel Fe-Ni catalytic ceramsite filler(Fe-Ni CCF)was prepared by the blast furnace dust which was a kind of solid waste generated in iron making.The CIP removal efficiencies of Fe-Ni CCF and troditonal Fe-C ceramsite filler(Fe-C CF)were compared.The results showed that Fe-Ni bimetal catalytic micro-electrolysis system greatly promoted the removal of CIP.Under the same conditions,CIP in wastewater was almost completely removed after degradation by Fe-Ni CCF abOTU 24 h,which was significantly higher than than the traditional Fe-C CF(75%).The study also proved that the blast furnace dust was suitable as the raw material of Fe-C ceramsite,which not only provided a new way for the resource utilization of blast furnace dust,but also reduced the processing costs.Secondly,the applying additonal dc power also greatly enhanced the performance of Fe-C micro-elecrolysis for CIP removal.The removal rate of CIP was increased by abOTU 60%in electrolysis-microelectrolysis(E-ME)system compared with the single Fe-C micro-electrolysis.The optimal operating conditions of E-ME system were:the applying voltage was 15v and iron bar was used as the anode... |
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