PENGARUH BAKTERI PENGOKSIDASI BESI DAN BAKTERI PENGHASIL BIOFILM TERHADAP KOROSI LOGAM ST 37 DI WADUK CIRATA

• Main Author: Sigit, Nathanael
• Format: Final Project
• Language: Indonesia
• Subjects: Ilmu hayati ; Biologi
• Online Access: https://digilib.itb.ac.id/gdl/view/55354
• Institution: Institut Teknologi Bandung

The existence of human activities in the form of recreational and fishery activities causes corrosion to the metal of Hydroelectric Power Plant (PLTA) installation in the Cirata Reservoir, namely ST 37 metal. The corrosion rate that occurs in Cirata Reservoir in aerobic conditions reaches 0.28 mm/year and is classified as potential severe corrosion. According to research from El Faidah (2018), the microbes that cause corrosion found in Cirata Reservoir waters include the iron-oxidizing bacteria and biofilm-producing bacteria. The iron oxidizing bacteria group is able to accelerate corrosion by producing iron oxide deposits which are reactive to metals, while the biofilm-producing bacteria group is able to form a layer that creates a local anode and cathode. Therefore, this study aims to isolate and to confirm the presence iron-oxidizing bacteria and biofilm-producing bacteria from corrosioncausing bacterial candidates from a depth of 0.5 m in Cirata Reservoir waters and to determine the corrosion behavior of the community of biofilm-producing bacteria and iron-oxidizing bacteria on a laboratory scale. Heterotrophic bacteria and ironoxidizing bacteria were selected using R2A medium and Winogradsky medium, which is a specific medium to isolate iron-oxidizing bacteria. The isolated bacteria were then selected based on their ability to produce biofilms using 96 well plate microtiter assay at a wavelength of 595 nm and their ability to oxidize iron and accelerate corrosion by inoculating bacterial isolates into a liquid Winogradsky medium containing ST 37 metal for 14 days. Based on the results of the microbial characteristics selection, 3 isolates were selected using Principle Component Analysis. The isolate was used as an inoculum in the aerobic corrosion behavior test at a temperature of 25-27 oC and dark conditions for 30 days in Cirata Reservoir water medium. The data that collected were the corrosion rate using the weight loss method, biofilm weight, medium acidity level, total dissolved solid and the abundance of planktonic and biofilm cells. Sample collecting were carried out every 3 days. There were 13 isolates isolated from R2A medium and 2 isolates from Winogradsky medium. Based on the results of the microbial characteristics selections, isolates E, F, and O were selected (identification in the sequencing process). Isolates E, F, and O have the ability to oxidize iron which is shown by their ability to grow on Winogradsky medium. Isolates E and F can grow to an abundance of 105 CFU/mL and isolates O can grow to 107 CFU mL. Isolates F and O had the ability to form biofilms as indicated by the absorbance in 96 well plate microtiter assays which were 22 and 13 times higher than the abiotic controls, respectively. Isolates E and F were able to induce corrosion as seen from the corrosion rates produced in the Winogradsky medium which reached 23 ?m and 43 ?m per year. From the three isolates, 2 variations of the bacterial consortium were made to be used in the accelerated corrosion test, namely the consortium of E: F: O isolates (3: 1: 1 ratio) and E: F isolates (3: 1 ratio). E: F and E: F: O isolates vi produced corrosion with the highest rates reaching 7.4 ?m/year and 3.5 ?m/year after 3 days of incubation. Respectively, E: F and E: F: O isolates were able to increase the corrosion rate up to 5.3 and 2.3 times compared to the abiotic control, so it is concluded that the presence of E, F, and O bacterial isolates was able to accelerate the corrosion rate of ST 37 metal. The weight of biofilm on E: F: O isolate was 1.23 times higher than that of E: F isolate, so it is concluded that the presence of O isolate was able to inhibit the corrosion rate induced by E: F isolate through the biofilm it produced