The facilities at the Old Muckworks process the enormous quantities of chemicals and liquid pollutants in the waters of Hutta. Unfortunately, this “processing” doesn't necessarily clean the water. Although the facilities do prevent the planet from becoming entirely lethal to non-Hutt life, their primary job is to filter any valuable compounds from waste dumped into the swamps. These compounds are drained into enormous factory vats. Whatever useless chemicals remain afterward go right back into the swamp water.
The original Jiguuna Muckworks was replaced by new Muckworks‒built some distance west of town‒several decades ago, but the successor facility went into critical failure shortly after its installation. The “Old Muckworks” returned to use, and the name stuck.