Corrosion Mechanisms Of Reclaimed Water Pipes Under The Synergistic Effect Of Disinfectants And Microorganisms

The special reclaimed water quality make the microorganisms easily to multiply,proliferate and produce microbial corrosion in the distribution system.Disinfection is commonly used to control the microbial growth,while,which not only influence the biofilm formation but also significantly change the water quality,producing a comprehensive impact on the corrosion process.Thus,the corrosion mechanism of ductile iron pipes under the coupling effect of disinfectant and microorganism was studied in order to provide scientific foundation and theoretical support for the efficient operation of reclaimed water distribution system.?1?The biofilm formation and growth characteristics,the iron-oxidizing bacteria and sulfate reducing bacteria growth status on the Q235B carbon steel,ductile iron and 317L stainless steel surface were analyzed by bacterial counting method and scanning electron microscopy?SEM?.Combining with the polarization curve and electrochemical impedance spectroscopy?EIS?,the corrosion promotion or inhibition effect of this mixed biofilm on the different metal were revealed,and the corresponding corrosion process concept model were also established.?2?The effect of different concentrations of NaClO and ClO₂ disinfectant on the corrosion products and corrosion process of ductile iron pipes were investigated by weight loss method,polarization curve,EIS and SEM.The results show that ClO^-and ClO₂ can replace O₂ participate the cathodic depolarization process and promote the corrosion process.?3?Based on the Annular Reactors?ARs?,the effect of different concentrations of NaClO and ClO₂ disinfectants on the microbial diversity of the main water and corrosion scales were studied by high throughput sequencing technology.The relationship between the microbial diversity of the main water and the corrosive scales was also analyzed.The cell damage status and physiological characteristics were characterized by flow cytometry combing with the different staining methods,aiming at analyzing the effects of different concentrations of Na ClO and ClO₂disinfectants on the cell apoptosis in the reclaimed main water.?4?The corrosion mechanism of reclaimed water pipes under the coupling effect of disinfectants and microorganisms were revealed based on the self-designed corrosion electrochemical test device for the flow system,which pointing out that the NaClO and ClO₂ promote the electrochemical-microbial corrosion process by changing the water quality?pH,DO,ORP,Cl^-,electric conductivity?and the proportion of Iron Oxidizing Bacteria?IOB?,iron reducing bacteria?IRB?and Ammonia Producing Bacteria?APB?in the corrosion scales.Finally,the three-dimensional response surface model between disinfectants concentration?NaClO,ClO₂?,microbial content in the corrosion scales and the general corrosion rate was established.