The production in the pulp and paper industry requires large amounts of water. The German Wastewater Ordinance implies that the resulting effluent has to be tested on the content of chemical oxygen demand (COD). In comparison with conventional testing methods the use of online COD analyzers offers high savings and also enables efficient water management.
In the steel industry water is of high importance. It is used for
As heat is used in any manufacturing process of the steel industry, the major need of water is for cooling purposes of the various facilities such as the furnace body and the actual products.
Less than 10% of this water is actually consumed. The majority is reused in recirculating systems, for example, when wastewater from direct cooling is recycled back after adding make-up water. Another way to improve water efficiency is to recycle wastewater and cascading water use from higher to lower quality.
Water effluents are those waters that cannot be recycled back even after treatment. Steel plants that aim for zero discharge of water effluents will treat the water to enhance its quality and use it for example in raw material dust suppression. Other plants will treat the effluents to comply emission limits in order to discharge it back to natural sources such as rivers and lakes.
Nevertheless, the monitoring of the water quality is crucial for efficient water circulation and safe plant operation.
The manufacturing process of pulp and paper requires huge amounts of water. The major part of this process water is recycled within a closed water system used for
To prevent an increase in concentration and a loss of quality of the ingredients, a small amount of wastewater is discharged, which is then replaced by fresh water.
During paper production about 10 m³ liters wastewater is produced per 1 tonne of air dried product, during pulp production it is about 40 m³ wastewater per 1 tonne pulp.
Wastewater from pulp & paper manufacturing is characterized by
In the effluent of a paper mill, the monitoring of COD or TOC is of importance to determine the organic load. It is the only way to identify production losses easily and buffer problematic loads. The wastewater treatment plant operators can better estimate the required cleaning performance and control it efficiently. The COD can also be determined by correlation with TOC (total organic carbon).
Additionally, the parameter TN (total bound nitrogen) is recommended for monitoring because an optimal cleaning performance needs a certain ratio of nitrogen and phosphorus. Furthermore, the wastewater toxicity should be tested. Chemicals such as biocides or chlorine, which are added to avoid mold, can significantly affect the biology of a wastewater treatment plant.