The Southeast Wastewater Treatment Plant processes wastewater from the central and eastern parts of Carbondale and from the Southern Illinois University Carbondale campus. The waste is discharged to Crab Orchard Creek. The plant was upgraded in 2005 from 3.19 millions of gallons per day (mgd) to 6 mgd with 12.5 mgd max flow.
In fiscal year 2017, the plant installed two variable speed drives on the oxidation ditch for increased efficiency. Also, two raw pumps were rebuilt which increased efficiency by 10 percent.