Membrane Bioreactor Treatment Characteristics Of Ciprofloxacin Wastewater And Changes In Resistance Genes In Sludge

Ciprofloxacin(CIP)is a broad-spectrum antibiotic.It accounts for large percent among antibiotics which are used nationally.Its detection rate is high in the environment.It has characteristics of strong biological stability and refractory biodegradation.It will cause damage on ecological safety and people's health by inducing resistant genes with microconcentration.So,it is critical to control its environmental emission.MBR is an efficient wastewater treatment equipment which has higher processing efficiency comparing with traditional biological processing techniques in terms of the antibiotic removal.CIP production wastewater contains high concentration of CIP.The concentration is as high as mg·L-1 to dozens of mg·L-1.This research adopts the MBR to treat simulated CIP production wastewater in order to inspect the change of activated sludge concentration and the removal characteristics of ammonia(NH3-N),chemical oxygen demand(COD),total organic carbon(TOC)and CIP with different CIP concentration.It also analyzes the removal pathways of CIP based on mass balance and the change of resistant genes and microbial communities.The results are shown that:(1)The tendency of sludge concentration is reduced first and increased after be balanced with increasing influent concentration of CIP.It is related that activated sludge is adapted to CIP and the long SRT.(2)As a result of increasing influent concentration of CIP,the removal rate of ammonia is continuously decreased which means the activity of nitration is inhibited,the overall removal rate of TOC is stable with slightly decreased,the removal rate of COD is gradually decreased which results from the inhibition of activity of microorganisms and the damage of cell.(3)According to mass balance,the main removal pathways of CIP are biodegradation,adsorption.The trend of biodegradation is decreased and then increased.The specific adsorption rate is increased and then decreased with increasing influent concentration of CIP.(4)From the study of resistant genes,it is shown that the four resistant genes of CIP are gyr A?gyr B?parC and parE.The tendency of these genes are all decreased firstly and and then increased and the gyrA and gyr B change obviously.(5)It is revealed that CIP has an effect on species abundance and population diversity of microorganism with the increasing CIP concentration and stress time by the results of high-throughput sequencing.It is also shown that the smaller of the unit of microbiology,the more obvious of the numberal change of microflora by CIP from the analysis of the results of phylum,class,order,family and genus.