Effect Of Concentration Rate Of Power Plant Circulating Cooling Water On SRB Biofilm Corrosion To Metals

In this paper, SS316L and SS304 were material for research, a strain of sulfate-reducing bacteria was isolated from reclaimed water of a Beijing thermal power plant circulating cooling-water system, and the reclaimed water was used in the experiment. The paper study on the SRB growth characteristics in the typical water regeneration, the influence of water quality factors on the growth of SRB biofilm、XPS spectra analysis of SS316L surface biofilm、biological membrane electrochemical corrosion behavior in the stainless steel material surface、the corrosion morphology and the analysis of composition changing under stainless steel biofilm surface, and get the following conclusions through experiments.The result showed that this strain of SRB can grow in reclaimed water, and the increase of ionic strength by concentrating the reclaimed water can promote the growth of SRB. Quality factor influence test showed that when the rate of SO42-/Cl- of reclaimed water was 1.5, the removal rate of SO4- was highest; SO4- reducing rate of power plant bacteria increased with NH4+-N concentration of reclaimed water.XPS analysis results showed that forms of Fe were Fe2O3 and Fe3O4 (Main ingredients of passivation film) in 1-3d, was FeOOH in 7d, was FeS2 in 14d; There were compounds of Fe2+ in the reclaimed water concentrated 3 times for ld-3d, but iron oxide appeared in the reclaimed water. In 7d-20d, the content of S and Fe compounds were further increasing in the reclaimed water concentrated 3 times environment, the compound form were FeS and FeS2. The chemical corrosion behavior of the power plant bacterial biofilm on the surface of the SS316L lasted longer in the reclaimed water concentrated 3 times environment. There was Si compounds on the surface of stainless steel specimen enrichment in the reclaimed water concentrated 3 times environment for 3d immersion time, but in 7d in the reclaimed water. The mole percentage of C compounds and O compounds were at the peak value on 7d immersion time, but 14d in the reclaimed water, the corresponding energy functional groups were C-C、C-H and C=O. Extracellular polymer organic compounds for hydrocarbon of Plants generate bacteria growth metabolism containing alkyl and carbonyl compounds, esters or alkane derived compounds, etc. Changes of ionic strength affected the formation speed of sediment and extracellular polymer, mixture cover earlier SS316L surface in high rate of reclaimed water.The SEM/EDS experiments showed that there were pitting corrosion on the surface of SS316L specimens immersed in the reclaimed water, pitting corrosion was more serious over time. After the reclaimed water was concentrated 3 times, the corrosion of the dense biofilm to stainless steel was growing after immersion 20d, in the same time there were more pitting corrosion pits.Corrosion electrochemical behavior results showed that Rp is reduced, in turn Vcor increased with the increase of concentration rate for the same immersion time. Along with the increase of the ionic strength, the membrane layer of power plant bacteria biofilm was denser, corrosion rate of SS316L surface increased. For the same immersion time i0 of SS304 electrode was nearly 10 times as much as io of SS316L electrode, Vcor was greater than the SS316L electrode, these suggested that the corrosion resistant of SS316L is better than SS304.