Directional Acclimation And Sonication Of Activated Sludge Accelerates The Monooxygenation Of Quinoline

Quinolion is a typical nitrogen-containing heterocyclic compound.Its molecular structure is a combination of a benzene ring and a pyridine ring.It belongs to refractory organics.Studies have shown that the initial step in the quinoline bioreaction is two mono-oxygeantion reactions that requires electrons and oxygen.The reactions are the control steps for the biodegradation of quinoline,and the second mono-oxygeantion reaction is slower than the first step.In this study,For the two monooxygenation reactions,directional acclimation of activated sludge to obtain the specific electron transport carrier which accelerated the second-step monooxygenation reaction of quinoline;Then the sludge was pretreated by ultrasound to accelerate the monooxygenation reaction of quinoline..The results of high-throughput sequencing of two kinds of directional acclimated activated sludge showed that there were differences in microbial community diversity between the two types of activated sludge.Scanning electron microscopy of untreated and ultrasonic treated sludge showed that the two cell types were obvious different;mixing the ultrasonic treated sludge with untreated sludge can significantly increase the biodegradation rate of quinoline,based on this case a first-order hybrid kinetics model is proposed.The main conclusions of this study are as follows:(1)Two kinds of activated sludge with different microbial communities in oriented culture have accelerated degradation characteristics of their target pollutant,which can accelerate the two monooxygenation reactions in the biodegradation of quinoline respectively;and when the two pollutants are present in the wastewater simultaneously,activated sludge can still preferentially degrade target pollutants.After high-throughput sequencing analysis of the two microbial communities,it was found that the diversity of activated sludge with quinoline as the target contaminant was slightly lower,and the dominant bacteria such as Thermomonas Rhodococcus accounted for the majority of the population,while the diversity of activated sludge with 2-Hydroxyquinoline as the target contaminant was higher,and there were rare strains.(2)Scanning electron microscopy shows that the sludge cells have not been ultrasonicated are more rounded and smooth;however,the ultrasonically pretreated activated sludge cells are deformed to varying degrees and the edges of the cells appear angular.Low-intensity ultrasound can stimulate the microbial activity of the sludge,making part of the flocs and bacterial micelles of the sludge broken up,freeing the microorganisms,and enhancing the transport of the substrate and oxygen.In the process,inactivation and activation occur simultaneously.Therefore,ultrasonically treated sludge can still biodegrade quinoline,and at the same time,some cells break and release organic matter and increase dissolved COD in water.(3)Experiments with ultrasonic treatment and untreated sludge showed that the amount of sludge was in the range of 800mg/L to 4000mg/L(dry weight),and the degradation rate of quinoline was proportional to the amount of sludge,and with the increase of sludge biomass,the acceleration effect of ultrasonic treatment sludge is more obvious than that of untreated sludge.(4)Accelerating the biodegradation rate of quinoline was more obvious when adding ultrasonic treatment sludge than adding external electron oxalic acid.From the calculation of the electron equivalent,it was found that the ultrasonically treated sludge supernatant added was equivalent to 3.04 mM oxalic acid.The results of this calculation show that the ultrasonically treated sludge can be used as a more efficient source of electrons to accelerate the biodegradation rate of quinoline and provide a theoretical basis for future engineering practice.(5)The experiment of degrading quinoline by ultrasonic treatment and untreated sludge resulted indicated that under the condition that the total amount of sludge is the same,the mixed sludge degradation rate of quinoline was much faster than the two separate sludge degradation rates.This is because the ultrasonic treated sludge not only acts as an electron donor in this process,but also play a role in biocatalysis with some intracellular substances and enzymes released by cell disruption,and the degradation rate of the mixed sludge fits the kinetic model very well.