The year-long project, which represents a £6m investment, will see the site's capacity increased in line with population growth in the area and help to maintain the highest possible standards of environmental protection to the area, including the River Wear.
Work, which is due to begin on site on March 23, will be carried out by Northumbrian Water's partner, Interserve Construction Limited.
During the first two weeks of the project, upgrades will also be made to the site's access road, including at the junction of the A689 to the east of the town. This will require traffic lights on the A689 to ensure the safety of workers, while a minor diversion will also be placed on the Weardale Way walking route.
For the remainder of the project, while a small increase in traffic to the site may be noticed, all work will be contained within the sewage treatment works.
Brian Ford, Northumbrian Water's Project Manager, said: "The upgrade of Wolsingham Sewage Treatment Works represents a significant investment in protecting the environment, including the River Wear.
"We are confident that residents and those who use the stretch of the A689 to the east of the town will see little disruption beyond the short term traffic lights in the coming weeks."
Anybody who wants to keep track of the project can do so at www.nwlcommunityportal.co.uk.