Detection and Analysis of Microbial Influenced Corrosion in Cooling Tower of Shahid Mofateh Power Plant

Abstract

Abstract Introduction: The water of cooling tower for Shahid Moftah power plant is supplied from treated wastewater. Therefore, chemical control of water in order to control corrosion in this cycle is very complicated. Methods: The results of the TBC (total bacteria count) test of cooling tower indicate the approximate number of bacterial colonies equal to 103 cfu/ml, which is in the light range. According to the microbial tests, the amount of TRB, IRB and APB bacteria is very high and has values ​​of 1200, 500-2300 and 105 cfu/ml, respectively. Using treated wastewater as a feed of cooling tower due to the presence of high concentration of calcium ions leads to intensification of sedimentation and increase the growth of microbial organism. Moreover, the presence of high nitrate is predictable due to the origin of water supply, which causes the increase of nitrate and nitrite reducing bacteria (NRB). On the other hand, the presence of high phosphate and sulfate in the sample increase sedimentation and intensify microbial growth, especially sulfate-reducing bacteria (SRB) in the sample. Findings: As a result, high concentrations of TRB, IRB, and APB bacteria is required to be selectively removed in the first priority. In the second priority, nitrate and sulfate ions, which are food for NRB and SRB bacteria, need to be removed by selective removal of nitrate ions using ion exchange resins and sulfate with biological regeneration method. Due to the high level of microbial agents TRB, IRB and APB as well as the high concentration of microbial agents feed, as the third priority, methods based on non-oxidizing biocides needs to be applied in this power plant.

Keywords

• microbial corrosion
• shahid mofateh power plant
• corrosion prevention
• total bacteria count
• corrosion monitoring