Biological Oxidation Of PH₃ Offgas:Process And Mechanism

PH₃is the lowest state compound of phosphorus and widely exist in natural environment such as wetlands,swamps,water body and aquatic sediments,it also comes from yellow-phosphorus production,refuse landfill,sewage treatment,grain fumigation and other human activities.As a highly toxic gas with foul odor,PH₃offgas seriously pollutes the environment,endangers human health and results in adverse effects on the subsequent production process,then the purification of PH₃offgas has been payed more attention than ever.At present,the biological treatment for PH₃ offgas with low concentration exhibits the advantages of simple operation and low costs,but the key factors for biopurification process and the mechanism of biological oxidation are seldom reported.In this study,the key indicators like PH₃ biological oxidation process of microbial growth and metabolic activities,organic matter transformation,ROS production,lipid peroxidation and oxidase activity were investigated,in addition,the transfer and transformation of PH₃ into biochemical system were investigated.At the same time,the addition of specific respiratory chain electron transfer inhibitors explored the inhibition factors of the purification process and ROS scavengers were added to the biochemical process to promote the biological oxidation of PH₃,and then,the process and metabolic model of PH₃ in microbial system were elucidated.Firstly,PH₃ by microbial floc adsorption to the surface,and then through the cell membrane into the cells,after biochemical metabolism process is oxidized to phosphate and phosphite,these low-priced phosphates were eventually oxidized to phosphate and react with ADP to generate ATP.Phosphorus migration and transformation processes are called biosorption and biotransformation according to their characteristics.In the biosorption stage,the adsorption capacity of PH₃ was about 0.062 mg/g of biomass,during the bioconversion stage,the concentration of orthologous phosphate in each reactor did not increase significantly during the whole test process,and the value was usually less than 0.9 mg/L.When fulvic acid and the tea polyphenol were added bioreactors not only can increase the permeability of the membrane,and also with the system of Fe³⁺,Cu²⁺and other metal ions react by covalent bonds to form stable complex.When the metal ions were transported into the organism,the activities of SOD and CATase oxidase in the two reactors（R1 and R2）were significantly enhanced by ROS scavenger.The average SOD enzyme activity of R1 and R2 reactors were 15.0,14.9 U/g,and average CATase enzyme activity were 20.5,19.6 U/g,respectively.Compared with the blank control system without ROS scavenger added,the O₂^-·concentration in the R1 and R2 reactors decreased to 12.5 and 6.8μmol/L,the PH₃ removal rate was increased to 80%-85%,and the PH₃tail gas bioconversion efficiency was significantly enhanced.The addition of fulvic acid and tea polyphenols can remove and alleviate the oxidative stress caused by ROS in time.The PH₃biological purification system that operates stably for a long time maintains a relatively complex and diverse microbial community.The largest abundance of microorganisms in the level of the genus is mainly Cellulomonas,Neosphingosine,Microbacteria,Ralstonia,Burkholderiaceae,Rhodobacter and so on.This study determined the concentration of hypophosphite(H₂PO^2-,+1),phosphite(HPO₃^2-,+3)and phosphate（H₂PO₄^-,+5）in PH₃biological purification system under typical working conditions Changes,explored the changes of different valence states of phosphorus compounds,preliminary exploration of phosphine biooxidation pathways,and also provide a reference for the geochemical cycle of the earth’s environment.