In an exclusive interaction with Paper Mart, Mr. Felix Sahayaraj, Commercial Head & Director – India, Kemira Chemicals India Pvt. Ltd., highlights the significant variation in water consumption across mills manufacturing different paper grades. He notes that brown grade paper mills typically operate within 2–5 m³/tonne of paper, while recycled based duplex board mills consume around 8–10 m³ /tonne. On the other hand, integrated mills producing fine paper require substantially higher water usage, ranging from 40–50 m³/tonne. He further emphasizes that robust online monitoring systems, combined with well-managed ETP operations, are critical to maximizing water reuse while consistently ensuring high-quality paper production.
Paper Mart: Based on current industry experience, what is the realistic lower limit of freshwater consumption achievable in practice, and what factors ultimately define this limit?
Felix Sahayaraj: Brown paper grade based mills operate at around 2-5 m³/tonne of paper, which is a significantly lower level of water usage. Technological implementation can further improve the quality of paper like reduction in chemical consumptions, and elimination of odour from paper etc.
The recycle based duplex board mills typically consume about 8–10 m³/tonne of paper while integrated paper mills producing fine paper grades have significantly higher water consumption, generally around 40-50 m³/tonne of paper.
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PM: In mills operating with high levels of water reuse, what operational and water quality challenges typically emerge?
FS: High level of TDS, conductivity prompts the mill to use higher chemical dosage. However, many mills prefer less chemical usage in the wet-end sections. In addition to this, most of the mills producing brown/ recycled paper grades face the odour problem, preventing them from exporting paper to other countries.
PM: After implementing conventional reuse and treatment technologies, what technical or process factors limit further reduction in freshwater consumption?
FS: High levels of TDS and conductivity in process water compel mills to increase chemical dosing, which in turn demands additional water for dilution, effective distribution, and other applications—thereby constraining further reductions in freshwater consumption. Moreover, in recycled or brown grade paper production, excessive reuse of process water often leads to odour-related challenges caused by the accumulation of anaerobic bacteria, formation of volatile fatty acids (VFAs) and hydrogen sulfide in closed-loop systems, resulting in unpleasant odours in the final product. To mitigate these issues and maintain paper quality, mills typically limit the extent of water reuse, ensuring the production of high-quality, odour-free paper.
Effective ETP treatment….combined with the use of high-quality polymers and robust online monitoring and control systems, can significantly enable mills to lower water consumption without affecting paper quality.
PM: In highly closed-loop systems, why does periodic purging remain necessary, and what determines the minimum freshwater requirement?
FS: In order to have good-quality paper and lower chemical consumptions, regular purging of water is essential for the paper mills. Some mills use anaerobic digesters to have good control over the recycled water. However, even anaerobic treatment has limitations due to high levels of calcium concentration in the paper manufacturing process.
PM: In mills already operating under high reuse conditions, how does monitoring and control help maintain system stability and manage water quality limits?
FS: Online monitoring of all process parameters, along with well-controlled ETP plants help the paper mill to maintain high reuse of water and achieve good quality paper simultaneously.
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PM: What types of technological or process improvements can help mills operate safely at lower freshwater consumption levels than currently achieved?
FS: Effective ETP treatment incorporating primary, secondary, and tertiary treatment stages, including clarifiers, anaerobic and aerobic biological systems, and advanced processes such as RO, combined with the use of high-quality polymers and robust online monitoring and control systems, can significantly enable mills to lower water consumption, without affecting paper quality.
