Research Of The Corrosion Of Recycled Water Pipelines By Sodium Hypochlorite And Sulfate Reducing Bacteria

Pipeline corrosion would not only affect the water quality,but also cause the waste of transportation energy.Sulfate reducing bacteria is one of the main strains in corrosion scale,and sodium hypochlorite can not only kill microbes,and corrode pipeline.So the study is important that the corrosion mechanism of sodium hypochlorite and SRB corrode the reclaimed water pipeline.The main content of this paper is to simulate the actual pipe network,in the anaerobic environment adding SRB and maintaining sterile conditions,the dosage was0,3,6,9 mg/L of sodium hypochlorite for corrosion,and in 1,3,4,5,6,7,8,10,11,13 and 15days,electrochemical test was doing by electrochemical workstation,every two days to determine pH,sulfate and total iron concentration.The structure of the fouling layer were observed by canning electron microscope after 15 days.The main conclusions are as follows:?1?The corrosion potential is affects by pH.pH was maintained stable by SRB to a certain extent.?2?Chloride involved the corrosion process of metal,and the biofilm formed by SRB can hinder the reaction between chloride and metal.?3?The existence of sulfate can promote iron corrosion and iron release.SRB can reduce sulfate to sulfur,then combined with Fe²⁺generation FeS,promoted corrosion.?4?Sodium hypochlorite can reduce the open circuit potential of metal,but high concentration of sodium hypochlorite had opposite effect because of the formation of a dense oxide film on the surface of the metal.?5?Under sterile conditions,the stability of nodular cast iron and the corrosion rate is proportional to the concentration of sodium hypochlorite.The corrosion rate will not increase when the concentration is more than 6 mg/L.It is suggested that sodium hypochlorite dosage is 6 mg/L to reduce the corrosion meeting the disinfection requirements.?6?The Nyquist of nodular cast iron had two capacitive arcs after 15d corrosion.The mass transfer diffusion became the key step to control corrosion with the fouling layer became denser.The corrosion products is porous produced by sodium hypochlorite.Under the scanning electron microscope,the crystal is mainly flake,the fouling layer is more dense produced by SRB,and its crystal form is spherical or flake,and the surface exist extracellular polymeric flocculent.