Sulphate Reducing Bacteria Water Analysis

Sulfate-reducing bacteria (SRB) is an anaerobic microorganism. It is widely found in anoxic environments such as soil, seawater, river water, underground pipelines, and oil and gas wells. It can use organic matter on metal surfaces as a carbon source and reduce sulfate to hydrogen sulfide using hydrogen produced within the bacterial biofilm.

Fig.1 Inhibitory mechanism of low pH on SRB. ^[1]

Formation of Sulfate-reducing Bacteria Corrosion

In some environments, sulfate-reducing bacteria (SRB) are able to accumulate on pipe walls, making it possible for localized pitting corrosion to occur. Sulfate-reducing bacteria react with organic material and sulfate to produce hydrogen sulfide and carbon dioxide will react with iron in the pipe wall to produce different forms of iron sulfide. Iron sulfide and other forms of deposits in the pipeline form a large amount of black powder, these black powder than the pipe carbon steel hardness, so it will cause serious corrosion hazards to the pipeline components.

Hazards of Sulfate-reducing Bacteria

Contamination of instruments and control valves

Scaling may lead to poor measurement results, and corrosion can lead to damage to components.

Contamination of clogged filter systems

When the piping system contains excessive amounts of black powder, which may lead to shortened filter life.

Contamination of pipelines

Increasing the roughness of the inner surface of the pipeline, which may cause severe or uncontrolled corrosion to the point of pipeline failure.

For SRB, water is the main factor for its presence and metabolic activity to occur. Reducing the corrosive effects of SRB requires control or elimination of water vapor in the pipeline and control with appropriate biocides.

Detection of Sulfate-reducing Bacteria

BOC Sciences offers analytical testing services for sulfate-reducing bacteria in water. Since the hazards and damages caused by biocorrosion of SRB are enormous, before SRB can be controlled and eliminated, SRB testing needs to be performed in relevant situations where corrosion may occur to determine whether SRB is present and at what levels, so that an appropriate treatment plan can be developed.

Detection Techniques for Sulfate-reducing Bacteria

1. Culture method

The main culture methods are the test bottle method, the agar deep culture method and the lysed agar tube method. These methods are based on the parallel extinction dilution method in the subsurface injection water analysis method.

2. Immunological method

This method is based on APS reductase, an enzyme that catalyzes the reduction reaction of adenosine-5'-phosphate sulfate reductase and produces a specific product of interest. Using the strength of the color reaction between this product and the chromogenic agent and comparing it with the colorimetric card, while getting the results of the sample in a short time, the test results are easy to observe and suitable for use in field testing.

3. ATP method

Adenosine triphosphate (ATP) is a compound that is present in all living biological cells, and its content is proportional to the cell concentration. The ATP released after cell fragmentation reacts with fluorescein, and the corresponding bacterial content can be determined. So you can indirectly determine the number of SRB by detecting the ATP content in the water sample, but the method can only detect the total number of microorganisms, so the lower limit of detection is high and not applicable to water samples with low SRB content.

4. Metabolite quantification method

The metabolite quantification method determines the SRB content by the amount of SRB metabolite sulfide production, which is simple to operate.

SRB Detection System

SRB assay system is a device for rapid detection of SRB by enzyme immunoassay method. The assay uses high purity antibodies to detect APS and has many advantages over cell capture techniques, such as rapidity and accuracy, providing a semi-quantitative result in a short period of time.