Summary
In power generation, pipeline, refining, and industrial water systems, biofilm does its damage out of sight. Bacteria carried in cooling and process water settle on wetted metal, bind themselves in an extracellular matrix, and within days form a layer that insulates heat transfer surfaces, narrows flow paths, and establishes the local chemistry in which microbiologically influenced corrosion (MIC) begins. The conventional check on that process — measuring how much biocide residual remains in the water — describes the bulk fluid, not the metal. A system can carry a satisfactory residual while a film thickens on the tubes, and the first dependable evidence often arrives as lost condenser performance or a through-wall leak.
On-line monitoring changes what the operator is actually looking at. The BG5 Biofilm Growth Detector measures biofilm activity electrochemically, at the surface itself. Its probe carries a stack of stainless steel or titanium discs that is intermittently polarized to a pre-set DC potential; as biofilm colonizes those discs, more applied current is required to reach that potential. Once a film is established, the probe also registers current the biofilm generates on its own during intervals when the applied potential is switched off. Both the applied and the generated currents are proportional to biofilm activity, producing a direct and continuous reading of surface condition rather than an inference drawn from chemical concentration.
That reading is what makes a treatment program adjustable. With activity trending in real time, chemical concentrations and addition frequencies can be matched to what the system actually needs, and cleaning and maintenance schedules can be set by condition instead of by the calendar. Under-treatment announces itself as rising activity in time to initiate mitigating action before significant damage is incurred. Over-treatment becomes visible as chemical spent without measurable effect — an avoidable operating cost that also carries a corrosion and environmental penalty. Alarm outputs and the controller communication options put that information in front of chemistry and operations staff without a trip to the probe.
Biofilm monitoring sits within the equipment and plant monitoring capabilities of SI’s Operational Support Services organization, alongside sample panels, chemical injection systems, and telemetry. SI’s process chemistry consultants pair the instrument with open and closed cooling water assessments and program change management, while the Metallurgical Laboratory provides deposit analysis and root-cause failure examination when fouling has already progressed to material loss. Probe materials, mounting arrangements, and controller ratings are published in the BG5 specifications sheet.