It was 40 years ago today — Sept. 25, 1978 — when the Western Lake Superior Sanitary District began operating its sewage treatment plant in Duluth.

“The network of pipes and pumps and tanks and treatment pools and chemistry all contributed as designed to clean harmful bacteria and other pollution out of the sewage — from not just Duluth homes, but also homes from surrounding areas and industry as far away as Cloquet,” writes Duluth News Tribune reporter John Myers.

Duluth News Tribune: “WLSSD marks 40 years of cleaner St. Louis River”