The microbiological management of process water ensures production continuity and quality in paper manufacturing. A new biological approach, alternative to traditional biocides and based on the use of beneficial microorganisms, makes it possible to control biofilm and reduce deposits. The results are improved operational stability, higher production efficiency, and enhanced environmental sustainability of industrial water circuits.
The quality of process water represents one of the most critical elements in ensuring production continuity in a paper mill, as well as guaranteeing machine stability and finished product quality.
The increasingly widespread recirculation of water has led to significant organic loads within paper production systems. High microbiological contamination in circuits can result in slime accumulation, unpleasant odors, and frequent machine shutdowns for cleaning operations, with inevitable downtime and increased operating costs.
For these reasons, it is necessary to adopt water treatment programs that are simultaneously microbiologically effective, environmentally sustainable, and economically advantageous.
Speaking about innovative solutions and future trends in water treatment is Andrea Cerasaro, Sales & Technical Manager and Product Manager at CHT Group, who addressed this topic at Miac 2025.
Conventional biocides
Historically, microbiological control in paper mill circuits has relied on oxidizing or non-oxidizing chemical biocides, explains Cerasaro. Among the most commonly used compounds are bronopol (2-bromo-2-nitro-1,3-propanediol), DBNPA (2,2-dibromo-3-nitrilopropionamide), chlorine and active bromine, and DDAC (didecyldimethylammonium chloride). These substances are well-established in industrial use.
As the manager points out, “they are products commonly used in the paper production cycle but, if not managed correctly, they can become potentially harmful chemicals”. In addition, evolving European regulations are progressively restricting the use of certain molecules, pushing the sector toward alternative solutions.
Beyond these aspects, conventional biocides also have an intrinsic limitation related to their mode of action, namely the indiscriminate elimination of bacterial populations. This often creates microbiological imbalances that favor the rapid regrowth of resistant species, making continuous dosing and frequent hot chemical cleaning cycles (boil-outs) necessary.
Probiotic water treatment
The solution developed by CHT proposes a paradigm shift in water treatment by introducing an innovative concept. “Our new approach is to replace conventional biocides with probiotics” explains Cerasaro.
Defined by the World Health Organization (WHO) as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host” — which by analogy can be considered the industrial system — they are natural, non-GMO, non-pathogenic bacteria already present in nature, used to restore biological balance within water circuits.
The concept developed by the group is based on the use of these microorganisms and the probiotic treatment technology, which redefines traditional water and machine cycle treatment. Its functionality is based on a natural and ecological process.
“Probiotic bacteria enter the system and degrade the biofilm matrix that slime-producing bacteria form as a defense” explains Cerasaro. In practice, these microorganisms feed on the carbohydrate-based biofilm that coats and protects pathogenic or undesirable species. These are precisely the organisms responsible for slime formation and other deposits that cause typical machine cycle problems.
The degradation of the biofilm exposes the undesirable microorganisms and creates unfavorable conditions for their survival. “At the same time, probiotic bacteria occupy available surfaces and compete for nutritional resources. This phenomenon prevents recolonization by problematic species, including those responsible for odor formation or deposits”.
The result is a microbiologically stable surface, free of slime accumulation and characterized by a controlled and harmless bacterial population (Figure 1).
The product used in paper mills, derived from this technology, is called Biotikos 100. “It appears as an opaque, milky liquid, with a pH close to neutrality when diluted at 10%”.
From a regulatory and safety perspective, the formulation complies with the main international regulations—FDA, BfR, and EU Ecolabel. Tests also indicate the absence of irritating or sensitizing effects on skin and eyes. Therefore, it is not only “a product that is safe to handle and apply,” says the manager, but it also “has all the necessary certifications for approval” a particularly relevant aspect for health, safety, and environmental managers in industrial plants.
Fields of application
CHT’s probiotic treatment can be applied in several areas: industrial and technical water systems, cooling towers, paper machine cycles, and deinking plants, where “it can replace glutaraldehyde used to inhibit catalase activity” explains the manager.
“Typical dosage ranges between 0.01% and 0.10%, but it is defined on a case-by-case basis depending on the level of microbiological contamination and the characteristics of the circuit”.
A fundamental prerequisite for applying the new technology is the complete elimination of conventional biocides before starting the treatment. “A standard biocide would kill the probiotics” Cerasaro clarifies, rendering the system ineffective.
This is followed by an initial saturation phase, usually started after a boil-out, with higher dosages aimed at rapidly colonizing the circuit. Subsequently, the dosage is optimized for continuous maintenance.
Monitoring treatment effectiveness is based on operational indicators agreed with the paper mill. Among the main KPIs, the manager mentions oxidation-reduction potential (ORP or Redox), pH, and temperature.
Monitoring is supplemented by visual inspections at critical points prone to bacterial growth and, if necessary, by the use of metal surfaces to check for possible slime-forming deposits. This method allows better evaluation of the entire machine circuit and timely intervention if problems arise.
Benefits of the system
The benefits of the treatment primarily result from the biological transformation of organic material. “Probiotics convert residues into non-odorous volatile compounds, such as carbon dioxide, avoiding the formation of acids responsible for bad odors, including sulfur compounds and organic acids like butyric acid”.
The competition for nutritional resources, as described earlier, progressively reduces populations of undesirable microorganisms, including sulfate-reducing bacteria and those that may cause Legionella, while the continuous consumption of biofilm prevents the formation of new deposits.
For paper mills, the most relevant benefit concerns production. From a manufacturing standpoint, all this “translates into fewer paper breaks and extended intervals between chemical cleaning of the plant”.
The probiotic method in the paper mill
Biotikos 100 was tested at Cartiera del Vignaletto, a company in the Veneto region with a strong focus on environmental and safety issues. Specifically, the probiotic technology was applied on tissue machine TM5.
Dosing was carried out at a single point, in the fan pump feed tank (the primary water circuit), and operational data were analyzed over thirteen months of continuous treatment.
“During the initial phase, a lower ORP potential was observed, followed by fluctuations also due to instrument calibration” explains Cerasaro (Figure 2). “Conductivity and temperature remained substantially constant throughout the entire period, confirming process stability” (Figure 3).
The results achieved represent one of the most significant aspects of the application. “Before the introduction of probiotic treatment, breaks attributable to microbiological slime ranged between twelve and sixteen per month. After system start-up, these breaks were completely eliminated”.
Considering that each shutdown resulted in an average loss of 10–15 minutes and that one hour of lost production corresponded to approximately €5,000 in paper costs alone, the economic return was estimated at about €20,000 per month (Figure 4). “Application costs are comparable to the previous treatment, but the production benefit is significantly higher”.
Moreover, after seven months without boil-outs, the headbox was clean and free of significant accumulations, leading to positive effects on formation profiles and a reduction in paper defects.
The adoption of CHT’s treatment enabled the paper mill to achieve more stable paper quality and a clear increase in productivity. “The absence of microbiological slime reduced defects per reel below previous standards and simplified machine start-up operations”.
Operational management was also simplified. As highlighted by the manager, the system requires only dosing via a dosing pump, without the need for preparation or preliminary dilutions. The only requirement concerns circuit preparation, which must be cleaned with a hot chemical wash, as application on heavily contaminated systems may initially cause massive slime detachment, leading to temporary sheet defects.
Developments and ongoing projects
The success of the application on TM5 at Cartiera del Vignaletto led, starting in 2024, to the extension of the technology to the plant’s second machine, TM4. “We have fully consolidated the customer’s trust” emphasizes Cerasaro, noting that health, safety, and environmental managers also expressed complete satisfaction with the new technology and its results.
While the treatment has been operational at the Veneto site for over a year, further applications are already under development. A new case study is planned at a paper mill using 100% recycled paper as raw material, with start-up scheduled for 2026.
The experience of Cartiera del Vignaletto demonstrates how probiotic treatment represents an applicable and effective evolution in industrial water management. The biological approach enables cleaner circuits, reduced use of potentially hazardous chemicals, and simultaneous improvement in productivity and environmental sustainability.
The technology developed by CHT therefore introduces a different operational model, based on creating a stable and controlled microbiological ecosystem. As Cerasaro summarizes, “we don’t eliminate bacteria: we replace them with the right ones”.
Italian evolution
Cartiera del Vignaletto was established in 1966 in Zevio, near Verona, with a cylinder machine dedicated to the production of creped papers for hygienic use, with an initial capacity of approximately 6 tons per day.
Ten years later, the company became a joint-stock company, embarking on a path of structured industrial growth.
The 1980s were characterized by the installation of new machinery. Increased customer demand and diversification led to technologically advanced plants and expanded production capacity. The real expansion occurred with the new millennium: growing market demand, including international markets, led in the early 2000s to an expansion of the facility to a total area of 30,000 m² and daily production of 135 tons of paper.
During the same period, the M.A.I.N. plant was established in the province of Matera, dedicated to the production of thermobonded and multibonded airlaid materials for feminine hygiene products, diapers, and medical applications.
Today, the paper mill produces tissue paper in rewound and laminated reels up to four plies, with basis weights from 15 to 45 g/m², intended for various products, using two tissue machines: one with double wire and one crescent former, both with a usable width of 280 cm.