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About Wastewater

Urban Water Cycle Story

Typically, we think about the water cycle as evaporation, condensation, precipitation, and saturation. How do humans fit into this cycle? The urban water cycle starts with our drinking water source and ends with treated wastewater going back into the environment. It includes the water flowing through a system of color-coded pipes underground. The pipe color (blue, green, purple, or black) indicates the type of water in it. What is the urban water cycle story in Thurston County?

Drinking Water

The story of the urban water cycle begins with your drinking water in blue-colored pipes. Most of Thurston County’s drinking water is high quality groundwater that requires minimal treatment. The water is naturally stored underground in an aquifer, which is a layer of porous rocks full of water. This water is pumped out of the ground through public and private wells.


After the water is used in our homes, schools, and businesses, it goes down our drains or toilets, becoming wastewater. Wastewater contains pollutants and must be cleaned before being released back to the environment. Our sewer system is a series of green pipes and pump stations that moves most of the urban wastewater to LOTT’s treatment plants.

At the treatment plants, the wastewater passes through a series of physical and biological steps to remove the trash, solids, and microbes. The majority of the treated water, or effluent, is released into Budd Inlet. The rest of the water is cleaned further to produce Class A Reclaimed Water, highly treated wastewater that is safe for irrigation and other non-drinking uses.

LOTT’s Wastewater Treatment Process

Homes not connected to the sewer system treat their wastewater with a septic tank. Septic systems are made up of a tank and drainfield. Solids settle in the tank where bacteria break them down. Liquids flow to the drain field into the ground where microorganisms in the soil help clean the wastewater. Septic tanks need to be pumped every three to five years. The pumped solids are taken to a wastewater treatment plant. Septic systems are effective at treating wastewater in rural areas, though too many tanks close together can pollute streams and groundwater.

Septic Tanks in Thurston County

Reclaimed Water

Reclaimed water is used water that has been treated and cleaned so it can be reused safely for irrigation and other non-drinking purposes. LOTT uses different technologies to make reclaimed water – sand filtration and membrane filtration. If you see purple pipes or sprinkler heads, you know reclaimed water is in use.

Reclaimed Water Treatment Systems

Groundwater Recharge

Groundwater is naturally recharged by rain and snow melt. Reclaimed water can also replenish groundwater through direct injection or natural infiltration. At LOTT’s Hawks Prairie Ponds and Recharge Basins, reclaimed water circulates through a series of five constructed wetland ponds before entering shallow basins where it soaks slowly into the ground. Slowly the reclaimed water reaches the aquifers. This is a solution to maintain or increase the reliability of local water supplies.


Stormwater is water from rain or melting snow that “runs off” land or impervious surfaces, such as paved streets and parking lots, into storm drains and black pipes. It picks up pollutants along the way including pet waste, fertilizers, and car oils. Depending on the storm drain location, the water may go untreated to the nearest body of water. Some storm drains connect to special treatment ponds where the pollutants are naturally filtered out. Polluted stormwater runoff is the number one source of toxic pollution in Puget Sound.

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