Biological Effluent Treatment

Introduction of stepped water circuits with a biological heavy-duty sewage plant for cardboard production

A recirculation water purification plant was taken into operation to close the in-house water cycle at Kartonfabrik Rieger GmbH & Co. KG. It consists of two series-connected pulp catchers and a flotation unit at the primary treatment stage, and a flotation-filtration pulp catcher at the secondary treatment stage. The clear water generated at primary treatment has a solids content of 240 mg/l, while the super-clear water produced at secondary treatment has a solids content of 10 - 30 mg/l and is deployed instead of fresh water. About 6,5 l wastewater/kg paper is achieved. A biological high-intensity unit that works according to the HCR (high-performance-compact-reactor) process was taken into operation for final biological treatment of the wastewater resulting from production. The following values are achieved in the outflow (average 1994 values): COD concentration: 878mg/l; BOD concentration: 267mg/l; Solids content: 74mg/l These values do not comply with the required standards. In order to meet the required outflow values, a conventional aeration unit has been installed downstream from the HCR plant. 

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Source: Environmental library of the Federal Environment Agency (UBA)