Anaerobic Treatment of Evaporator Condensate in Combination with Caustic Extraction Liquor From a Pulp Industry, 1993 Environmental Conference Proceedings

An anaerobic full-scale plant treating the wastewater from a dissolving sulphite pulp industry corresponding to 60 tons of COD is in operation, at Borregaard Industries Ltd, Norway. The wastewater is a combination of sulphite evaporator condensate (SEC) and caustic extraction liquor (CEL), mainly of the dissolving type. A maximum of 50% of the COD originates the CEL. The AOX content in the CEL is about 16 mgA.

Two years of pilot plant studies, and results from the full-scale plant, demonstrate that the anaerobic contact process, ANAMET, developed for treatment of wastewaters from sugar factories can be applied to wastewaters from the pulp and paper industry.

To treat this combination of SEC and CEL with 50% of the COD content from CEL, an adaption of the sludge is necessary. If the adaption is successfully performed, the COD content from CEL can be even higher than 50%. With a combination of 50% COD from SEC and 50% COD from CEL in the wastewater the reduction of COD is 65%, BOD 88% and the reduction of AOX is 40%.