Sewage & Waste Water Facilities are operating in various stages. The sewer mains flow into progressively larger pipes until they reach the wastewater treatment plant. In order to help gravity do its job, the wastewater treatment plant is usually located in a low-lying area, and sewer mains will often follow creek-beds and streambeds (which flow naturally downhill) to the plant.

Once the water reaches the wastewater treatment plant, it goes through one, two or three stages of treatment (depending on the sophistication of the plant). Here's what each stage does:

The first stage, known as primary treatment, does the same thing a septic tank does. It allows the solids to settle out of the water and the scum to rise. The system then collects the solids for disposal.

The second stage, known as secondary treatment, removes organic materials and nutrients. This is done with the help of bacteria. The water flows to large, aerated tanks where bacteria consume everything they can. The wastewater then flows to settling tanks where the bacteria settle out. Secondary treatment might remove 90 percent of all solids and organic materials from the wastewater.

The third stage, known as tertiary treatment, varies depending on the technology used, and the composition of the wastewater. Typically, the third stage will use chemicals to remove phosphorous and nitrogen from the water, but may also include filter beds and other types of treatment. Chlorine added to the water kills any remaining bacteria before the water is discharged.

Sludge (Biosolids) Treatment:

STEP 1  The "primary sludge" from the Primary Settling Basins is pumped to the Hydrocyclone Grit Separator where it is spun, thereby separating the inorganic solids (grit) from the lighter weight organic solids. The grit is usually disposed of in the City landfill.

STEP 2  The primary sludge continues on to the gravity Sludge Thickener where the solids are concentrated and pumped to the anaerobic digesters. The liquid overflow is returned to the pump station. Waste Activated Sludge from the Final Settling Basins is pumped to a Centrifuge for further solids processing, then pumped to the anaerobic digesters (digester tower).

STEP 3  Primary and activated sludges are anaerobically digested and decomposed by bacteria without the presence of air.  Stabilized sludge has little odor and conforms to the EPA requirements to further reduce harmful microorganisms.

STEP 4  Methane gas is produced by this anaerobic digestion and is used as fuel for a cogeneration CHP power plant producing electrical and thermal energy heating the treatment plant buildings and to provide heating to improve the sludge digestion process and produce more gas. Surplus energy is fed into the public electricity grid.

STEP 5  Step 5 is the application of the stabilized sludge (biosolids) onto farmland by subsurface injection (plowing). The biosolids are utilized in an environmentally acceptable manner as a beneficial and valuable fertilizer and soil conditioner.