# Sustainability in Italian Ceramic Tile Production: Evaluation of the Environmental Impact
## 3 Results
### Water and Waste Management  
Recycling and reuse of materials are fundamental missions for the Italian ceramic tile industry. Water is almost completely recovered within the production process after some purification steps. Recycled water is used for all the working operations which do not necessitate high levels of purity, as milling and spray-drying phases and washing of machineries and facilities. Water recycling is made possible by the absence of hazardous elements in the waste waters. However, water coming from glaze preparation and decoration phase (frits and pigments treatments) cannot be easily recycled due to the presence of ions in the used solutions. Figure 8 shows the water balance inside a ceramic plant; the main sources of waste waters outlet are represented by the vapor of the gaseous effluents from the firing and by the water involved in the spray-drying stages. The values for the R\({}_{\text{H2O}}\) indicator reported in Figure 9 show the percentages of water recycled for the three production classes. The reference values for the recycling ratio of water set by the EU Ecolabel and the Italian BAT legislations are 90% and 50% respectively. The trend highlights an optimized management of water used in ceramic tile plants. Values higher than 100% (as reported for Class 2) are due to the tendency of certain plants to collect wastewaters from other production sites. This is  
Figure 8: Scheme of the water balance of a ceramic tile plant. Figure 7: Emission trend for the emission factors for NO\({}_{\text{x}}\) (EF\({}_{\text{NOx}}\)). related to the fact that production plants belonging to Class 2, producing an excess of spray-dried powders, can recycle high amounts of water in a process that does not require high level of water purity. In fact, the rheology of the ceramic slurry, even if sensitive to flocculation and aggregation events, can always be tailored by adding low-cost additives, such as polyphosphates [32]. When a complete water recycling cannot be pursued, wastewaters are filtered and chemically treated with coagulants and flocculants to achieve an optimum degree of clarification. The obtained ceramic sludges may eventually be landfilled or disposed for the appropriate inertialization treatment if the level of hazardous substances exceeds the legal limits. However, also these sludges can be recycled within the production process, as reported in the scientific literature [49; 50]. Another important parameter for the sustainability of a ceramic tile production plant is the recycling ratio of solid waste. This environmental indicator considers the discharged green and fired tiles as well as ceramic powders coming from final surface treatment operations. The remaining waste sources cannot be considered in this data collection because of the existence of a proper legislation regulating both their recycling and their disposal. However, the mentioned materials represent the main solid wastes produced in ceramic tile plants. Green tiles, that have been discharged from the production process, are easily recycled inside the mills for the preparation of the ceramic slurry, thanks to the similar mineralogical composition. A different recycling management occurs for fired materials; cracked or deformed tiles that have already been fired and the ceramic powder coming from final surface treatments as squaring or smoothing, are usually employed in small amounts in the body formulations [51]. Indeed, their introduction in the mix shall be carefully monitored in order to avoid rheology variations of the ceramic slurry and undesired shrinkage in the new production. Figure 10 highlights the values for the recycling ratio of solid waste, R\({}_{\text{SW}}\), over a period of 9 years. The trends demonstrate how a complete recycle for the solid waste is accomplished for all the three production classes. As it happens for the water management, the plants belonging to Class 2 show values of the indicator always higher than 100% as they usually collect solid ceramic wastes from other ceramic industrial plants.