Study On The Corrosion And Sterilization Mechanism Of SRB On 304 Stainless Steel In Reclaimed Water

In this paper the growth characteristics of SRB which was isolated from the sludge at the bottom of cooling-water tower and the bio-film in real reclaimed water are studied, using ATCC-7757 as a comparison. The corrosion behaviors of SS304 by SRB and the bio-film are studied. The sterilization effects on sulfate-reducing bacteria (SRB) of three kinds of bactericides which are commonly used in industrial water treatment:NaClO, isothiazolinone and 1227 was analyzed.SRB after the separation and purification has the same characteristics of ATCC-7757. Both of them can grow well in real reclaimed water, but SRB has better adaptive than ATCC-7757, and the corrosion of stainless steel is more serious in real reclaimed water with SRB.The SEM/EDS experiments showed that the corrosion of stainless steels was pitting in the early, and then became large. It showed that bio-film formed by SRB on the surfaces of stainless steels consisted of SRB, metabolism substance and corrosion products in the late. The corrosion behaviors of SS304 stainless steel were investigated by measuring EIS. The results showed that the electrochemical characters of corrosion are because of the biofilms, corrosion product films and metabolism substance. Due to the biological membrane thickening, the changing of resistance and capacitance is unstable. The biofilm on the surface played a role of inhibiting corrtion to some degree in the early time. The decrease of polarization resistance and electric capacity value of SS304 was due to the breaking of passive film by the corrosion products, and the localized corrosion was accelerated in the late.NaClO, isothiazolinone and 1227 all have the bactericidal effect of SRB and ATCC-7757 in reclaimed water, but SRB was more sensitive. The most effective bacteriacide of them is 1227, and the inhibit bacterial of 1227 can continue about one week. The SEM/EDS experiments showed that NaClO, isothiazolinone and 1227 all can hinder the formation of biofilms, but the degree was different. Although NaClO had the function of sterilization, its decomposition products may cause corrosion of stainless steel. In addition to sterilization,1227 had the capacity of anticorrosion and antismudgy by forming membrane on the surface of stainless steel.