Process for recovering chemicals from wastewater including an oxidative pre-treatment

摘要

The method for the recovery of chemicals from sewage that arises during the production of fibrous material from lignocellulose raw material under use of sulfur salt, comprises subjecting the sewage to an anaerobic sewage treatment for producing sulfur and/or sulfur compounds. The sulfur salt contained in the sewage is oxidized by adding chemicals, before the anaerobic sewage treatment. Air, oxygen and/or ozone are introduced into the sewage containing the sulfur salt. The sewage from oxidation causing fibrous material-bleaching step is mixed with the sewage containing the sulfur salt. The method for the recovery of chemicals from sewage that arises during the production of fibrous material from lignocellulose raw material under use of sulfur salt, comprises subjecting the sewage to an anaerobic sewage treatment for producing sulfur and/or sulfur compounds. The sulfur salt contained in the sewage is oxidized by adding chemicals, before the anaerobic sewage treatment. Air, oxygen and/or ozone are introduced into the sewage containing the sulfur salt. The sewage from oxidation causing fibrous material-bleaching step is mixed with the sewage containing the sulfur salt. Additional oxidation causing chemicals are added.