POTENSI KOMUNITAS BAKTERI AEROBIK DARI WADUK CIRATA SEBAGAI AGEN BIOKOROSI

• Main Author: Vasya Rahmani, Fadhilah
• Format: Final Project
• Language: Indonesia
• Subjects: Ilmu hayati ; Biologi
• Online Access: https://digilib.itb.ac.id/gdl/view/54295
• Institution: Institut Teknologi Bandung

Corrosion is a redox reaction between metallic surfaces and their environment. There are several types of corrosion. One of them is biocorrosion, which is a type of corrosion that is induced by microbes. Aerobic biocorrosion can be induced by several bacterial communities, such as iron-oxidizing bacteria (IOB), sulphuroxidizing bacteria (SOB), acid-producing bacteria (APB), and EPS-forming s one of the power plants with the potential of experiencing huge economical losses due to biocorrosion. Previous fieldm depth were capable of inducing corrosion 1,39 times faster than of 10 m. Therefore, this study is focused on determining the corrosion rate and roles of aerobic bacterial community from Cirata Reservoir at a depth of 0,5 m and 10 m in inducing corrosion on ST37 carbon steel on a laboratory scale for 30 days with analysis from data collected every 2 days. The medium and inoculum used in this analysis carried out included biofilms and corrosion products on ST37 carbon steel, biofilm and corrosion product weights, corrosion rate, pH, HSconcentration in the medium, as well as the total abundance of planktonic and biofilm bacteria using the Total Plate Count (TPC) method on R2A Agar medium. Visualization of biofilms and corrosion products in 0,5 m and 10 m samples showed that the biofilms from both depths indicated Fe3+ compounds presence in the biofilms, which are the products of IOB metabolism, with biofilms from samples of 0,5 m depth observed to be thicker than 10 m. In addition, there is also another corrosion product on the steel from 0,5 m samples with a blackish color, which is thought to be FeS as a result of the reaction of sulfate-reducing bacteria (SRB) metabolites with iron. The average corrosion rate in 0,5 m and 10 m samples decreased with time, with the highest rate occurred on the 2nd day of incubation, which is 5,66 mm/year and 5,30 mm/year for 0,5 m and 10 m respectively. This result is classified as Severe Corrosion Potential based on the National Association of Corrosion Engineering standards. The total abundance of planktonic and biofilm bacteria did not have any significant difference between both depths, but the accumulation of biofilm occurred faster in 0,5 m samples compared to 10 m. The highest HS- concentration in the medium of 0,5 m sample occurred on the 4th incubation day with a concentration of 0,025 mM, while in 10 m it occurred on day 0 with a concentration of 0,019 mM. These results indicate a higher role of SRB. Higher pH reduction occurred in 0,5 m samples which indicates higher presence of APB in 0,5 m samples than in 10 m. The highest pH reduction in the 0,5 m samples was found on the 26th incubation day and in the 10 m samples was on the 14th. From the results of this study, it can be concluded that the corrosion rate of 0,5 m and 10 m are classified as Severe Corrosion Potential with the average corrosion rate for 30 days of incubation always above 0,25 mm/year. In the depth of 0,5 m, biocorrosion is induced by EPS-forming bacteria and IOB, SRB, and APB respectively, while in 10 m it is induced by SRB, EPS-forming bacteria and IOB, and APB respectively. Different bacterial communities at two different depths indicate specific corrosion processes and potentials.