LAR Process Analysers AG

Water analyzers for Pulp and paper industry - Pulp & Paper

The production in the pulp and paper industry requires large amounts of water. The German Waste Water 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.

Water in Paper Manufacture

In the manufacturing process of pulp / paper a lot of water is required. The major part of which is recycled. To avoid an increase in concentration and a loss of quality of the ingredients, a small amount of waste water is discharged, which is then replaced by fresh water.

In recent years, the industry was able to reduce the water requirements for the manufacturing process significantly. However, there is still an average of 10-11 l waste water per kilogramm of product produced in the course of the production. A complete avoidance of waste water is not possible even in a closed circuit.

Quality requirements, as well as problems such as salt formation or odor makes the draining of waste water necessary. Generally, this waste water is warm, mixed with fibers, highly contaminated with chemicals and relativly low in quantity.

Water Management

In the effluent of a paper mill, the monitoring of COD is very important. It is the only way to identify production losses easily and buffer problematic loads. The waste water 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).

Schematic view of a water- and sewage circulation in the paper and cellulose industry.

Additionally, the parameter TN (total bound nitrogen) is recommended for monitoring because an optimal cleaning performance needs a certain ratio of nitrogen and phosphorus. Further, the waste water toxicity should be tested. Chemicals such as biocides or chlorine, which are added to avoid mold, can significantly affect the biology of a waste water treatment plant.

Conventional COD test methods are time-consuming and cost-intensive. Hence, they are unsuitable for an efficient water management. Online measuring systems provide a remedy.