Study And Application Of Microbial Slime Growth Mechanism In Circulating Cooling Water System

The most common problems in industrial circulating cooling water system are scaling,corrosion and microbial breeding,which are closely related to the growth of microbial slime.In this study,the circulating water in the circulating cooling water system of Yanshan Petrochemical Company was taken as the sample,and the microbial slime was cultivated through the static circulating cooling water simulation test.In order to explore the growth mechanism of microbial slime in circulating cooling water system,the dynamic changes of cooling water system and microbial community structure in the growth process of microbial slime were explored,and the electrochemical parameters in the growth process of microbial slime were analyzed.Based on this mechanism,biomimetic mineralized materials were synthesized and applied to repair cement cracks.The main results are as follows:(1)The pH of circulating cooling water containing bacteria condition was higher than that of water without bacteria,and the change of mass per unit area under bacterial condition was larger than that under sterile condition,and the change of mass per unit area of the bacteria-containing hanging piece was greater than that of the hanging piece without bacteria.The concentration of inorganic salt ions in bacteria-containing and aseptic conditions showed the same trend,which basically increased first,then decreased and then increased.The concentration of inorganic salt ions in bacteria-containing condition was slightly lower than that in aseptic condition.The dominant bacterial genera in the microbial slime samples obtained at different cultivation period were Pseudomonas,Acinetobacter,Blastomonas,etc.The relative abundance of Pseudomonas and Blastomonas increased with the increase of culture time.The richness of microbial community and biodiversity reached the highest at the middle and late culture stages.At the same time bio-functions strengthened along with the culture time,like Fermentation,Dark oxidation of sulfur compounds,Ureolysis,could promote microbial corrosion and mineralization.(2)At the initial stage of cultivation,the polarization resistance R_p decreased with the increase of cultivation period under aseptic and bacteria-containing conditions.In the middle and late period of cultivation,R_p in aseptic condition increased first,next decreased and then increased,while R_p in bacteria-containing condition increased gradually.The R_p in the bacteria-containing condition was lower than that in the aseptic condition,and the biofilm resistance R_b in the bacteria-containing condition increased first then decreased,finally stabilized at 500Ω·cm~2.Some corrosion products were generated in the middle and late period of culture under both bacteria-containing and aseptic conditions,and some of them would fall off under hydraulic action.However,certain sediments were generated in the presence of bacteria,and dense biofilm structure was formed on the surface of carbon steel to preventing the corrosion reaction.With the change of cultivation period,the bioslime obtained under bacteria-containing condition will change from loose fine particles to dense bulk sediments,and the content of Fe,Ca and Mg in microbial slime will gradually increase.The content of Ca and Mg in microbial slime under bacteria-containing condition is much higher than that under aseptic condition.The presence of bacteria can promote the transformation of inorganic salt precipitate from amorphous structure to higher crystallinity structure in microbial slime.(3)The biogels prepared with polyacrylic acid,sodium alginate and chitosan as carriers contain a large number of K.oxytoca bacteria,which have strong vitality and can induce biological mineralization to prepare biomimetic mineralized materials.All the prepared biomimetic mineralized materials formed calcite.Among them,the biomimetic mineralized materials obtained with sodium alginate and chitosan as carriers also formed vaterite.These three biomimetic mineralized materials all have certain ability to repair cement cracks,fill indentations,and especially can achieve good repair effect in the case of small crack width.