Paper mills are high-water-consumption facilities. Process water circulates continuously through stock preparation, forming sections, press sections, and white water recovery systems. That constant warm, nutrient-rich water circulation creates ideal conditions for one of the most persistent and costly problems in the industry: biofilm.
Biofilm in pulp and paper mills is not a minor housekeeping issue. It is a direct threat to product quality, equipment integrity, and production continuity. Yet because biofilm is invisible in its early stages, most mills only become aware of it once it has already caused a problem.
What Biofilm Does in a Paper Mill
Bacterial biofilm establishes itself on any wetted surface in the water circuit: chest walls, pipe interiors, forming fabrics, press felts, suction rolls, and heat exchanger surfaces. In the paper machine specifically, biofilm causes four categories of damage.
The first is sheet breaks. Biofilm deposits that detach from surfaces and enter the paper web create weak points that trigger breaks on the machine. Each sheet break means downtime, wasted furnish, and the time and labour cost of re-threading the machine.
The second is holes and defects. Biofilm slime patches that reach the forming section create holes and inclusions in the finished sheet. In printing and packaging grades where surface uniformity is critical, this means rejected rolls and downgraded product.
The third is odour. Anaerobic bacteria within mature biofilm communities produce hydrogen sulphide and other volatile sulphur compounds. In tissue and food packaging grades, odour contamination is a serious quality problem that can result in customer complaints and product recalls.
The fourth is under-deposit corrosion. Biofilm creates localised anaerobic environments against metal surfaces where sulphate-reducing bacteria accelerate corrosion at rates far exceeding what the bulk water chemistry would predict. Headboxes, suction roll shells, and press section components are all vulnerable.
Why Conventional Biocide Programmes Often Fall Short
Most paper mills manage biological contamination with periodic biocide dosing. Oxidising biocides such as chlorine dioxide or peracetic acid are dosed on a schedule, sometimes supplemented with non-oxidising biocides. The intention is to maintain a bacteria-free system. The reality is often different.
Planktonic bacteria floating freely in the process water are relatively easy to kill with biocides. Sessile bacteria within an established biofilm are a different matter. The extracellular polymeric substance matrix that makes up the biofilm structure acts as a physical barrier, reducing biocide penetration to the cells beneath. Studies have shown that bacteria within biofilm can be 100 to 1,000 times more resistant to biocides than their planktonic counterparts.
This means that a biocide programme calibrated against bulk water bacterial counts may be systematically under-treating the biofilm that is actually causing the production problems. The mill is spending on biocides, but dosing blind.
The Monitoring Gap
Traditional microbiological monitoring in paper mills relies on planktonic bacteria counts from water samples, typically reported as colony-forming units per millilitre. These measurements tell you about the free-floating bacteria in the bulk water. They tell you very little about the state of the biofilm on process surfaces.
A mill can show acceptable planktonic counts in its water samples and still have well-established biofilm on forming fabric supports, in headbox manifolds, or on roll surfaces. The sample does not capture what is happening on the wetted surfaces that actually determine production performance.
Inline Biofilm Monitoring with the Alvim Sensor
The Alvim Biofilm Sensor addresses this gap directly. Rather than sampling the bulk water, the sensor measures biofilm accumulation directly on a representative surface that is in continuous contact with the process water stream.
The sensor uses electrochemical impedance spectroscopy to detect the earliest stages of biofilm formation on its sensing surface, providing a continuous real-time signal of biofilm development. This allows mill operators to:
Detect biofilm onset before it reaches the threshold at which it causes production problems, enabling intervention at the earliest possible point rather than after a sheet break or quality failure has already occurred.
Verify biocide effectiveness in real time. Rather than dosing on a fixed schedule regardless of whether biofilm is actually developing, the Alvim sensor shows whether a biocide treatment has been effective by monitoring whether biofilm accumulation stops or reverses following dosing. This closes the feedback loop that conventional planktonic counts cannot provide.
Optimise biocide consumption. Mills that install the Alvim sensor typically find they can reduce biocide spend by dosing in response to actual biofilm development signals rather than against a precautionary schedule. In a facility where biocide costs can run to significant sums monthly, this is a direct operational saving.
Identify problem zones. Multiple sensor installations at different points in the water circuit allow the mill to pinpoint where biofilm is establishing preferentially, whether that is in the white water circuit, the approach flow system, or specific machine sections.
A Measurable Improvement in Production Reliability
Paper mills that move from schedule-based biocide dosing to Alvim-monitored responsive treatment consistently report reductions in sheet break frequency, fewer quality rejections attributable to biofilm slime, and lower total biocide consumption. The sensor provides the visibility that converts a blind biocide programme into a targeted one.
For pulp and paper operations in Malaysia looking to improve machine efficiency and reduce the production losses associated with biological contamination, inline biofilm monitoring represents a practical and measurable step forward.
To discuss how the Alvim Biofilm Sensor can be integrated into your water treatment programme, contact us at info@autoflotechnology.com.