GROWTH EVALUATION OF SULPHATE-REDUCING BACTERIA (SRB) ASSOCIATED WITH BURIED MILD STEEL RODS

Abstract

Introduction: Sulphate-reducing bacteria are the major cause of corrosion of underground structure corrosion of underground structures made of mild steel.

Objective: This study set out to evaluate the growth pattern of sulphate-reducing bacteria associated with buried mild steel rods in Akure metropolis, Nigeria

Methodology: Mild steel rods (12 mm diameter, area 39.97 cm²), were collected from Ondo State Water Corporation (ODSWC), Akure, Nigeria and were buried and monitored for a period of three months. Percentage composition of the mild steel rods was determined. Isolation of sulphate-reducing bacteria was carried out using compounded Postgate C medium. Turbidimetric growth pattern and biochemical characteristics of the isolates were determined using standard protocols.

Results: Citrobacter freundii, Citrobacter gilleni, Enterobacter aerogenes, Pseudomonas aeruginosa, Desulfovibrio vulgaris and Bacillus megaterium were the bacterial consortia isolated from the buried mild steel rods. Turbidity was observed to be at low level on the 5^th day of sulphate-reducing bacteria (SRB) growth, but increased to optimum on the 10^th day of incubation and reduced drastically on the 15^th day. The growth outline of sulphate-reducing bacteria (SRB) was confirmed by the swelling turbid periodic growth for all four mediums. Iron (Fe) had the highest percentage mineral composition of 98.7 % whereas lanthanum had the least composition at 0.00031 %.

Conclusion: Findings of this study revealed the presence of sulphate-reducing bacteria (SRB) on buried mild steel rods of a water distribution system suggesting induction of corrosion of the underground mild steel pipes.