Where they thrive
SRB need three things: sulfate (present in most natural and process waters), an oxygen-free niche, and stagnation enough to keep it that way. Biofilms and deposit blankets supply the anaerobic zone even in aerated systems — which is why SRB damage shows up in firewater and hydrotest water left in lines, tank bottoms under sludge, dead legs, and buried structures in anaerobic clays.
Recognizing their work
The classic signature: black, sulfide-rich deposits with a rotten-egg odor over deep, localized pitting — often terraced or cup-shaped — on equipment whose bulk water analysis looks benign. The signature is an indicator, not a verdict: a defensible MIC diagnosis combines deposit microbiology sampled at the damage, pit morphology, and an operating history with a stagnation story.
Control
Deny the niche: drain and dry idle systems, remove deposits mechanically before chemical treatment (biocide through an established biofilm kills its surface layer and little else), verify with monitoring, and line chronically wet surfaces so the colony has no metal to work on.