Water quality demands in paper, chemical, food and textile companies
Sustainable water use in chemical, paper, textile and food industries
When optimizing water networks and increasing water efficiency an accurate definition of the required water quality is the key to achieve this goal. Poorly defined water qualities result in either problems with product quality, safety or in a sub-optimal water network. In the first case, the constraints for the water demands were set too loose, allowing higher contaminant levels than actually permitted by the process. The latter is the consequence of a conservative approach where water quality demands are set higher than required by the process. This report tries to give a global overview of water quality demands for common processes in each of the four sectors. These figures should be considered as guidelines when no other information is available and should not be implemented without thorough investigation. For the four sectors (paper, chemistry, food and textile) required water quality is defined based on the function of the water, not the origin, taking into account the different aspects involved in each sector (product safety, product quality, process stability, workers safety, etc.). In the paper sector most predominant water related problems are (bio)fouling and microbially induced corrosion on the one hand and scaling on the other hand. Most of the processes and products that are used create favourable circumstances for scaling and microbial growth. Chemical industry is known to produce a very diverse range of products, hence have a broad spectrum of processes which are applied. For many of these processes no references are available regarding required water qualities. In these cases the water quality needed was derived from the type of water which is commonly used and the possible interference of certain contaminants. The chemical sector was divided into 5 subsectors, for each subsector several processes are described. The aim was not to have a complete list of all chemical processes, but to at least give a representation of the processes for the most important chemicals used in Europe. In the food sector, the water quality which can be used in the different processes is always linked to product safety issues. Hence, many of these requirements are specified in national regulations. Nevertheless it is still possible to use water of lower quality when it can be guaranteed that product quality and product safety remain at the highest level. For textile industry critical water parameters and water usage of the different processes were described. The main issue here is the product quality and how this is affected by the quality of the inlet water. Also in this case, setting limits for certain parameters was found to be difficult as very often the affect on the process and/or the product is unknown.