Virtual Tour of Nine Springs Wastewater Treatment Plant

Primary Treatment

After being screened, the water flows downhill to primary settling tanks, which are designed to separate solids from the water. In these tanks, which are 12 to 15 feet deep, the water is slowed down to allow heavier solids to sink to the bottom and lighter solids, like fats and oils, to rise to the top.

Skimmer bars on the top and bottom of the tank periodically push the floating and settled solids to collection troughs at the end of the tank to remove them. In the 2-hour journey water takes through these tanks, about half of the solids are removed.

Secondary Treatment (aeration tanks)

The water moves on to 20-foot-deep aeration tanks for removal of additional solid matter and nutrients. Nutrients are necessary for life, but it's important to remove them from wastewater because in high levels, they can pollute water bodies by causing overgrowth of weeds and algae. In the aeration tanks, microscopic organisms (microbes) remove nutrients and solid matter from wastewater by consuming them as their food.

The mixture of microbes and solids, called activated sludge, includes microbes like bacteria, other single-celled organisms, and tiny animals like worms. The second picture above shows some microbes from the activated sludge under a microscope.

The aeration tanks are constantly bubbling from air forced into the tanks to provide oxygen for the microbes and keep them mixed up with their food. After 8 to 12 hours in these tanks, the water is ready to move on.

Final Clarifiers

A mixture of microbes and water leaves the aeration tanks through channels and enters final clarifiers, which are designed to separate activated sludge from clear water. In these tanks, the mixture is slowed down so the microbes start to clump together, becoming heavy enough to sink to the bottom of the tank. Meanwhile, water travels toward the edge of the tank. Collector bars slowly sweep around the top and bottom of the tank to collect remaining solids.

Most microbes that settle out of the final clarifiers are sent back to the aeration tanks to keep removing nutrients, while about 10 percent of them are sent to the solids processing part of the plant. The clear water continues to the Effluent Building.

Effluent Building

The final stop for water at the plant is the Effluent Building. During the warmer months, the water is disinfected in this building to reduce the amount of germs. Water passes through racks of light bulbs giving off ultraviolet (UV) light, which damages the cells of germs in the water so they are not able to multiply in the environment.

All year long, all treated water (effluent) passes through this building to be pumped several miles away to two streams, Badfish Creek and Badger Mill Creek. The water that leaves the Effluent Building is essentially river water. It's not clean enough to be drinking water, but it's clean and safe enough for fish, bugs, and plants to live in and for humans to swim, boat and fish in it.

Solids Processing

The solids removed from primary and secondary treatment have to go somewhere, too! Solids from the primary tanks and a portion of the sludge from the final clarifiers are pumped to the solids processing part of the plant, where the solids are thickened before heading into covered structures called digesters. In the digesters, bacteria break down the solids, which stabilizes them and reduces germs. After about 20 days in the digesters, the final product, called biosolids, is thickened and sent to storage tanks. The District calls its biosolids product Metrogro.

Metrogro Storage Tanks

After being processed, Metrogro is sent to large, domed structures to be stored. The District recycles Metrogro in the environment by applying it as fertilizer to local farm fields. Biosolids are rich in nutrients removed from wastewater, so they help crops grow. It's a win-win – the District is able to remove biosolids from the plant, and farmers get a natural fertilizer for their crops for free.

However, biosolids application is only possible at certain times of the year. Biosolids can't be applied on frozen ground or on top of snow, because they would just run off of the field with rain or melted snow and pollute nearby waterways. During times of year when it isn't possible to apply biosolids, they are stored in three tanks that each hold a little over 6 million gallons of Metrogro.

Metrogro Building

The District's Metrogro team is in charge of working with farmers to accept the biosolids and hauling them to their fields. When it's the right time of year for fertilizer application, the Metrogro team begins its hauling season, driving truckload after truckload of Metrogro to local fields and incorporating it into the soil.

The Metrogro building contains a mechanical workshop where the team maintains the large trucks used to carry and apply Metrogro to fields.

Control Room

Employees called operators are in charge of keeping the plant running as it should. Their home base is the Control Room, where computer monitors display all parts of the sewer system and the plant. The system alerts the operators if it detects anything out of the ordinary, like a low flow of water that might indicate a blocked or broken pump, so workers can fix the problem right away. Operators can control several parts of the system from the computer program, turning machines on and off as needed.

Operators are onsite every day of the year to keep the system working and prevent overflows of untreated wastewater.

Laboratory

The plant includes a lab where chemists test the water and biosolids to verify that they meet standards for quality and safety. District chemists perform over 1,000 tests a week to make sure that the water leaving the plant is low in pollutants like solids, nutrients, germs and metals. Lab results also tell the operators how the plant is performing at removing pollution, helping them make decisions about running the plant.

Badfish Creek

Most treated effluent – about 37 to 39 million gallons per day – is pumped to Badfish Creek. The water leaving the pipe tumbles over a stepped concrete structure, which is similar to a waterfall and mixes air into the water so it's healthy for fish and other wildlife in the stream. The place where effluent exits the pipe, called the outfall, is essentially the beginning of Badfish Creek.

Mississippi River

Believe it or not, the water that starts in our sinks and showers and toilets can end up in the Mississippi River. The streams that receive treated effluent eventually join up with the Rock River, which flows into the Mississippi near Davenport, Iowa.

Gulf of Mexico

The Mississippi carries water, including the same drops of water that passed through the treatment plant, to many communities along the river. Some communities use the river for drinking water, treating it to a higher quality so it's safe to drink. Eventually, the Mississippi passes New Orleans and flows into the Gulf of Mexico. Our use of water here in Wisconsin is connected to the ocean and to the people and wildlife downstream. It's up to us to keep water clean to protect it for those who will use this water next.