Black liquor

Purpose

During the chemical cooking of straw or wood, wastewater with high COD and high colour load is produced. This wastewater is treated using a biological process (fermentation, decanting). Even after this treatment, the wastewater still contains excessive colour and COD. The pollution caused by this wastewater is very high.

Solution

Retention of COD and of the main proportion of colour. Generation of a clear, reusable wastewater.
During treatment, the product is split into two phases:

• a filtrate with low colour and low COD content
• a concentrate, whose small volume contains the main proportion of COD and colour. The constituents of this part can be stored or easily incinerated.