Study On The Corrosion Characteristics Of Pseudomonas Monteilii Strain S30 And The Effect Of Microorganisms On Iron Release In Water Supply Pipelines

With the development of economy and the improvement of people’s living standard,the problem of water supply network has become a hot topic.Steel pipe and cast iron pipe are widely used in water distribution networks.After long-time use due to the physical,chemical,electrochemical and microbial influences,corrosion occur in water supply pipes.Corrosion of water supply pipes is not only the causes pipeline failure,but also promotes the deterioration of drinking water quality.Moreover,the pipe service life is reduced by corrosion.In the process of water supply pipe corrosion,pipe scales are produced.When the hydraulic and water quality conditions change,the pipe scales will be destroyed,resulting in the release of iron and pollution of drinking water.This paper focuses on the microbiological corrosion and iron release of water supply pipeline.Firstly,the pipe scale microorganisms were screened,isolated and purified to obtain Pseudomonas monteilii strain S30.On this basis,the influence of this strain on the corrosion process of cast iron pipe was studied.The effect of microorganisms on the iron release of water supply pipe was analyzed through static simulation experiment.The main contents include the following aspects:（1）TSA culture medium was used to screen cast iron pipe scaling microorganisms,and the separation and purification were completed.Strain identification was carried out by molecular biological method,and a kind of iron pipe scaling bacteria--Pseudomonas monteilii strain S30,which belongs to Pseudomonas family,and is called theγstrain.The bacteria were used to study the corrosion characteristics（2）The corrosion of feed iron pipe by Pseudomonas monteilii strain S30 at different nitrate concentrations was studied by simulation experiment.With the increase of concentration of nitrate,ammonia and nitrogen content increased,the content of total iron and ferrous iron decreases,in the experimental group containing bacteria liquid,with the increase of nitrate concentration,water content of total iron and ferrous iron decreases,when the nitrate concentration of 20 mg/L,the consumption of NO₃^--N is 5 mg/L,NO₂^--N,NH₄⁺-N generation 0.40 mg/L,4.40 mg/L respectively,ferrous iron and total iron content were 0.07 mg/L and 1.00 mg/L.（3）The corrosion rate changes under different conditions are similar:the corrosion rate increases in 0-60 days,decreases in 60-90 days,and tends to be stable in 90-170 days.The maximum and minimum values were 0.22mm/a and decreased to 0.07mm/a,respectively.The chemical composition of the scale in the four experimental groups all containα-Fe OOH,and the scale produced in the scale group containing the bacterial solution and the NO₃^--N 20 mg/L experimental group contains the most types,and it contains Fe₃O₄ structure.（4）The effects of changes in water alkalinity,SO₄^2-,Cl^-,p H and dissolved oxygen（DO）before and after reactor sterilization on iron release were studied by static experiments.The relationship between the total iron content of the reactor effluent and the influent SO₄^2-,Cl^-,alkalinity,dissolved oxygen and p H was consistent before and after sterilization.The total iron concentration of effluent is in direct proportion to the concentration of SO₄^2-and Cl^-of the inlet water,in inverse proportion to the dissolved oxygen（DO）and alkalinity,and is in parabolic relation with p H.Compared with before sterilization,the total iron release after sterilization of the reactor was reduced to a certain extent,and the total iron content of steel pipe and cast iron pipe could be reduced by14.44mg/L and 4.26mg/L,respectively,indicating that microorganisms could promote the release of iron in the pipeline to a certain extent.