Primary clarifiers

Above is the primary clarifier. While solids settle to the bottom, clear wastewater flows through a series of filters over the top on its way to the next step in the process.

Above is the primary clarifier. While solids settle to the bottom, clear wastewater flows through a series of filters over the top on its way to the next step in the process.

After being screened, the wastewater enters two 45-foot diameter, 140,000-gallon tanks called clarifiers. Here the biosolids are allowed to settle to the bottom of the tank. The solids are eventually pumped out of the tank and stored for later treatment. Between 15 and 40 percent of the solids are removed at this stage, which takes about 4.5 hours.