The paper and cardboard industry consumes large quantities of water (5m3 per ton of paper produced) and generates large volumes of wastewater with high polluting loads that affect water resources. These effluent discharges are loaded with different types of ink used for printing plates and contain low biodegradable substances such as pigments, solvents and other adjuvants.
Currently, approximately 20 million liters of water are used by this industry each year. Such excessive use, resulting essentially from the washing of the printing machines and the starch glue preparation tanks, required a high availability of water and has repercussions on the treatment of the generated effluents. A systematic study was conducted to reduce the amount of water consumed in the cleaning of flexographic printing machines. We used the response surface methodology that allows the analysis and modeling of the effects of factors involved in water consumption at the printing machines. This method has been widely used for the optimization of various processes in food chemistry, materials science, chemical engineering and biotechnology.
Experimental design methodology was used to design the experiments, to perform statistical analysis, and to determine the optimum conditions. Three factors, namely, cleaning program, color of ink used, and concentration of detergent used for cleaning were selected as variables, whereas the volume of consumed water was selected as the responses.