Continuous process control in paper mill wastewater treatment plants makes it possible to improve operational stability and treatment efficiency. The integration of online monitoring, data analysis, and predictive algorithms allows chemical dosing to be adjusted in real time according to variations in wastewater quality, reducing reagent consumption, sludge production, and effluent variability, while ensuring compliance with environmental limits.
In the management of paper mill wastewater treatment plants, process control makes it possible to ensure reliable performance and maintain it over time. However, it is essential to manage it properly, especially through continuous monitoring of operational variables.
Digital solutions are a precise and useful tool in the hands of paper mills, with some interesting innovations, such as those provided by Kemira. This was discussed at MIAC 2025 by Anders Ånäs, Global Digital Services Manager of the company.
Treating wastewater
Wastewater treatment is becoming progressively more challenging. According to Ånäs, “environmental regulations are becoming stricter every year globally, and this increases operational complexity for treatment plants.” At the same time, increasing production capacities in paper mills adds pressure on wastewater treatment plants (ETP – Effluent Treatment Plants). Moreover, the variability of wastewater characteristics makes management even more difficult. Changing operating conditions and growing production volumes continuously alter pollutant composition, and this—explains the Kemira manager—makes optimization of biological treatment complex, whereas such treatment requires stable conditions to function efficiently.
The solution adopted by many plants consists of “compensating for these variations through constant chemical dosing, but this method often leads to overdosing or underdosing, resulting in unstable effluent quality.” Furthermore, traditional monitoring based on daily laboratory analyses does allow dosing adjustments, but these often occur too late compared to process needs. “By the time the laboratory data arrives, the problem has often already occurred,” Ånäs notes, and this is one of the main limitations of conventional systems.
Therefore, performance improvement cannot rely solely on operational experience; it requires more precise and effective tools capable of providing continuous process control and timely, real-time intervention.
It is precisely in this context that digital solutions are introduced, designed to support data-driven chemical process management across all production stages.
Structured monitoring
The solutions developed by Kemira, Ånäs explains, are based on the integration of specialist consulting, application expertise, and advanced data analytics. The first step starts “with diagnostic and consulting activities, followed by the development of predictive models based on large datasets and machine learning algorithms”. The goal is to provide paper mills with digital tools capable of anticipating process deviations, where continuous monitoring and automatic control become key tools for transforming data into operational actions.
Specifically, Kemira’s monitoring and control system for water treatment is integrated into the KemConnect Water Treatment digital services. “The solution is based on two main pillars: high-reliability online measurements and automated chemical controls customized to the specific conditions of the plant. The goal is to stabilize water quality and keep the process consistently compliant with regulatory limits,” the manager continues. Monitoring units are installed throughout the treatment process—for example in sedimentation or flotation stages—to analyze both incoming water and treated effluent.
Real-time measurements include key parameters such as turbidity, suspended solids, dissolved COD (chemical oxygen demand), phosphorus, pH, and conductivity. This data feeds control algorithms which in turn automatically adjust dosing of coagulants, flocculants, and pH adjustment chemicals, enabling immediate response to changes in water quality. With this method, “we aim to make wastewater treatment a predictable and stable process,” Ånäs explains. “The key is combining reliable measurements with automated controls based on chemical expertise.”
The core of the system
At the center of the company’s service is Kemira SED, an advanced monitoring unit designed for real-time control of process and wastewater treatment plant performance. Currently, around 50 units are installed worldwide, the manager reports. It is a modular system that can be adapted to the specific needs of each facility. Kemira SED can analyze up to four samples simultaneously through a single unit equipped with an automatic cleaning system, ensuring continuous operation while reducing maintenance needs.
Among its features is a new method for sample pre-treatment developed to increase measurement reliability even under difficult operating conditions. Measurements are directly integrated with control algorithms that regulate chemical dosing according to the quality targets set by the paper mill. Continuous data availability also allows operators to remotely monitor the plant, enabling 24/7 control and timely intervention in case of deviations.
Application in a Northern European paper mill
An application example of Kemira’s system involves a paper mill in Northern Europe. The plant had difficulties maintaining effluent COD levels within permitted limits. “The plant was using high quantities of aluminum sulfate for chemical precipitation, resulting in high costs and inconsistent performance,” Ånäs explains. The owner’s goal was to stabilize effluent quality while optimizing treatment costs.
The solution implemented by Kemira engineers involved installing the Kemira SED unit with online turbidity and COD measurements, and developing a control algorithm specifically tailored to the plant’s needs. This enabled the mill to automatically regulate aluminum sulfate dosing based on target COD levels downstream of the dissolved air flotation (DAF) unit.
“Thanks to real-time measurements, the system was able to continuously adapt chemical dosing to actual operating conditions. It is not simply about automating dosing,” Ånäs emphasizes, “but about doing it based on reliable data and a control logic built on application experience.”
Comparison between the baseline period and the post-implementation phase showed significant improvements, the manager highlights. “Effluent COD load was reduced and, above all, aluminum sulfate dosing was halved while achieving higher COD removal.” Chemical process efficiency was effectively doubled, he explains, with positive impacts on both operating costs and overall plant sustainability. Reduced reagent consumption also led to lower chemical sludge production, contributing to a reduced environmental impact of treatment. The paper mill achieved more stable effluent quality, optimized chemical use, and gained greater operational transparency thanks to continuous 24/7 monitoring of the water treatment process.
Data as the foundation of water treatment
Wastewater treatment is now one of the main challenges for paper mills, especially in maintaining parameters consistently within permitted limits using traditional biological systems. Kemira’s experience shows how the combination of chemical expertise, online monitoring, and advanced algorithms enables a shift toward a predictive approach—capable not only of maintaining stable operating conditions over time but also of rapidly responding to changes in water quality. Continuous data availability and the speed at which it can be processed make this possible.
“The real value,” concludes Ånäs, “arises when chemistry and digital technology work together: data becomes an operational tool that helps plants become more efficient and sustainable.”