The paper industry has long been considered as one of the largest consumers of freshwater, with paper mills using significant amounts of water in various stages of production. Just a couple of decades ago, having a source of ample water and a suitable drainage point were the necessities before setting up a paper mill. The popular belief was that ten litres of water were needed to produce a one A4-size paper sheet.

However, with increasing environmental concerns and the growing need for sustainability, the Indian paper industry made serious efforts, including water recycling, system closure, and process upgrades to reduce fresh water consumption. As a result, most of the mills are now operating with water footprint levels at par with global standards.

The water-intensive nature of paper mills

Paper production involves multiple processes, including pulping, washing, screening and cleaning, bleaching, and paper forming, all of which require an optimum level of consistency to achieve the desired quality parameters. So, essentially, the whole process requires frequent dilution and dewatering (thickening) of paper pulp, thus leading to significant water consumption and wastewater generation. The discharge of untreated wastewater can result in water pollution, harm aquatic ecosystems, and pose regulatory challenges.

The action line

After a thorough study of ongoing mill practices, it became clear that the mills need to work in multiple directions to reduce fresh water consumption. Process upgrades were necessary to ensure equipment required less water or operated at increased consistency levels. Also, various screening and cleaning systems were upgraded, as a lot of water is also used in the paper machines for cleaning the machine’s clothing. For the same, improved showers with reduced nozzle sizes were installed. With a very small nozzle size, the problem of getting the nozzle choked with unwanted impurities even in freshwater was an issue. For a few such nozzles, even RO (Reverse Osmosis treated) water was used.

Not only this, recycling emerged as a potential approach, and at many points where fresh water was being used, it was replaced with recycled water. Wherever needed, in-situ treatment (kidney technology) was also used to ensure that the process control and product quality remained unchanged.

With the reduction in water consumption, the quality of wastewater is also changing. As freshwater consumption was reduced, there was a reduction in wastewater generation, and hence, to a certain extent, the pollutant concentrations increased. For the same, the government made it mandatory to have a fully functioning Effluent Treatment Plant (ETP) to ensure it is adequate by getting it verified by designated third parties like Central Pulp & Paper Research Institute (CPPRI) or Indian Institute of Technology (IIT). It was also mandated for each paper mill to establish a dedicated effluent treatment laboratory, and the records to be regularly sent to SPCB and CPCB.

To ensure that treated effluent always remains within norms, mills also installed a continuous online effluent monitoring system by which the effluent parameters like flow, BOD, COD, pH, TSS, etc. are being sent to the servers of SPCB and CPCB. In case of any deviation, automatic SMS and email alerts are generated to the mills, which need to submit the cause for the same and action taken report to them. Of course, this needed a huge capex but mills, considering it an environmental responsibility, went for this.  

The outcome of recycling water in paper mills

Well, the most significant advantage is a dramatic reduction in water consumption. Now, waste paper-based mills require just 25–50 ml of water to produce one A4-sized sheet of paper. For agro- and wood-based mills, the figure is around 100-150 ml on average. Several waste paper-based mills have reduced water consumption further and now are operating at Zero Liquid Discharge (ZLD).

Such steps have also resulted in cost savings for the mills, a significant reduction in pollution load, and increased regulatory compliance and environmental conservation. For the mills situated in water-stressed areas, conservation has helped to maintain groundwater levels.

Paper recycling promotes overall sustainability by decreasing dependence on natural sources of water. This makes the paper mill efficient and enables it to meet increasing demands for sustainable production.