From flush to the Mississippi
Editor’s note: This story is part of the Republican Eagle’s 2019 Progress Edition. This year we take readers “Behind the Scenes” of the sometimes hidden work of organizations around the area. Find the rest of the stories at Behind the Scenes.
Everyone uses water every day: washing dishes, taking showers, flushing the toilet, making much-needed morning coffee. As long as there is nothing wrong with the plumbing and the water bill has been paid on time, people may not think about where the water that spurts from the tap comes from or where it goes when the bottom of the coffee pot, the part with the loose coffee grounds, is dumped into the sink.
All of the water in Red Wing, residential, commercial and industrial, flows to the Red Wing Wastewater Treatment Plant. The plant, according to Bob Stark, Red Wing's deputy director of utilities, the wastewater system has three facilities:
"The main lift station at the east end of Levee Park, the main wastewater treatment plant on the north side of Barn Bluff, and the Industrial pretreatment plant at the waste campus on Bench Street."
The pretreatment plant processes between 300,000 to 400,000 gallons of water a day from the S.B. Foot Tannery, leached water from the landfill and wastewater from processing solid waste. All of the water eventually arrives at the main wastewater campus.
As soon as people step outside of the waste campus' office and lab building, they are met with a stench, a stench that gets stronger and stronger as they approach the tanks where water is cleaned. The smell curls nose hairs and chokes out any other smells in the area. It is similar to what the combination of methane gas, old sewage water and stale cat urine would smell like. But, maybe worse.
Tim Eickhoff, the chief plant officer, assured the group touring the plant that after working there for awhile, he is no longer able to smell the water that he is working to clean. He gave the analogy of hockey players: Eventually, they get used to the smell of their equipment and locker rooms and it no longer disturbs them.
The first step of the water treatment process is to remove large items from the water at the facility near Levee Park. Anything that is larger than a quarter of an inch in size, sand and grit is filtered out and sent to the solid waste campus.
The water is then sent to two primary clarifying chambers at the wastewater campus where it sits for six to 12 hours. As the water sits, solid particles sink to the bottom of the tanks and greases and oils float to the top. The "floaters" and "sinkers," as Stark refers to them, are removed from the water and are turned into sludge. Sludge, or biomass, is a good fertilizer. Instead of discarding the biomass, the wastewater plant partners with local landowners and farmers who use the biomass in their fields. According to Stark, about two to two and a half million gallons of sludge is produced a year. When the local landowners are unable to take the sludge, it is sent to treatment plants in other municipalities because Red Wing has limited storage for the biomass.
It takes about a day for water to go through the entire clarifying system, much of that time is spent sitting in order to separate water, floaters and sinkers. The main treatment, however, is done by bacteria.
Once the water has been separated from much of the non-water substances, it is sent to two trickling filters. Stark explained what happens in these filters:
"(Water) is sprayed on a plastic media that is covered with a biofilm consisting of bacteria and small protozoans. These organisms use the dissolved organic waste as a food source, thereby removing it from the wastewater. During this process, these organisms grow and eventually slough from the plastic media and are removed from the liquid wastewater in a second set of clarifiers."
The last step of the process is to treat the water seasonally with chlorine and then sulfur dioxide. Since the water is released into the Mississippi River, it cannot have chlorine in it because it would hurt fish and other organisms. So, the chlorine-treated water is treated with sulfur dioxide to remove any excess chlorine. As the water is released into the river, is flows over a small dam to increase the levels of dissolved oxygen.
The wastewater plant runs continuously and processes about 2 million to 2.5 million gallons of water a day. According to Stark, five people monitor the two plants. They work standard 9 a.m. to 5 p.m. jobs, but they always keep their phone and iPad with them to monitor the plants. Stark explained that if an error occurs, employees receive an alert on their phone and can log into their work computers from home. Once the situation is assessed, the employees can make some changes from home (such as shutting off a hose), decide to go to the plant, or decide that the problem can wait until the next morning to be addressed.
There are also a chemist and lab technician who work in a lab at the wastewater plant. Their job is to collect samples of the water and run a variety of tests. These tests include looking for: biochemical oxygen demand, total suspended solids, phosphorus, bacteria, chlorean, Ph, and dissolved oxygen. Test regularity (depending on what the water is being tested for) can vary from daily to once a year. Annually, the lab tests the water for toxicity. Water samples are collected and minnows are put into the water to ensure that they can live in the plant's treated water.