The Roles Of Pseudomonas Aeruginosa And Ensifer Adhaerens In Accelerating Nitrobenzene Biodegradation

Nitrobenzene(NB)is an organic compound widely used in industrial fields.Due to the high toxicity of NB to organisms,the random discharge of NB-containing wastewater in industrial production makes the receiving water body reach an unbearable level,and also seriously endangers the survival of aquatic organisms.Therefore,it is an urgent matter to adopt effective methods to treat wastewater containing NB.Compared with physical and chemical methods,the use of biological methods to treat NB-containing wastewater is a more economical and environmentally friendly treatment method for refractory wastewater.Among them,the use of bio-enhancement technology to accelerate the biodegradation of NB is one of them.However,there are still few studies on bioaugmentation to increase the degradation rate of NB and its mechanism,and further research is needed.NB itself is a toxic substance.In the process of biodegradation,it will inevitably be accompanied by changes in toxicity.With this as the theoretical basis,we can try to analyze the mechanism of bio-enhanced NB degradation ability from the perspective of toxicity.The main conclusions of this paper are as follows:(1)The strains Pseudomonas aeruginosa and Ensifer adhaerens were successfully screened from the activated sludge subjected to aerobic domestication,which can accelerate the biodegradation of nitrobenzene through bioenhancement.Although the dry weight of P.aeruginosa and E.adhaerens used in the experiment is only one-tenth of that of the domesticated activated sludge,their removal rate of nitrobenzene is 1.2times and 2.4 times that of the domesticated sludge,respectively.Adding P.aeruginosa and E.adhaerens to the domesticated sludge to degrade nitrobenzene can further increase the removal rate of nitrobenzene,and the removal rate is 1.4 times and 3.2times that of the domesticated sludge alone.(2)P.aeruginosa and E.adhaerens can alleviate the toxicity inhibition of o-aminophenol,an intermediate in the process of nitrobenzene biotransformation.When the domesticated sludge was used alone for the biodegradation of nitrobenzene,the toxicity increased in the first hour and then gradually decreased,during which the intermediate o-aminophenol was formed.Among them,o-aminophenol is more toxic than nitrobenzene.Compared with P.aeruginosa and E.adhaerens,o-aminophenol has a more obvious inhibitory effect on domesticated sludge.When P.aeruginosa and E.adhaerens are used alone for nitrobenzene biodegradation,the toxicity has been decreasing.(3)Although the abundance of E.adhaerens in the domesticated sludge in this study was only 0.01%,and P.aeruginosa was not detected,they showed a better ability to reduce the inhibition of o-aminophenol.This shows that if P.aeruginosa and E.adhaerens are used as bio-enrichment agents for enrichment,they have great potential to accelerate the biodegradation of nitrobenzene or similar compounds.