Wastewater Treatment

When you wash dishes, take a shower, pour stuff down your kitchen sink, or flush the toilet, that "wastewater" goes down a small pipe in your home to a bigger sewer pipe underground. The sewer pipes lead to a treatment plant, where wastewater is cleaned, and then returned to our river.

Longview's sewer system carries dirty household wastewater to the Cowlitz Water Pollution Control Plant to be treated to meet EPA clean water standards.

Cleaning Sewage

At the treatment plant, wastewater is allowed to settle into tanks, with the heavy "stuff" sinking to the bottom, and the dirty water rising to the top. The dirty water is removed to separate tanks where tiny creatures called microorganisms eat the wastes. A small amount of chlorine is added to kill remaining bacteria. Finally, the water is returned to the river.

Meanwhile, the heavy stuff, called sludge, is baked. Heating sludge kills harmful bacteria and breaks it down into water, carbon dioxide and methane gas.