Waste Water Treatment

One of my classes at UMD is about treating waste water at WLSSD (Western Lake Superior Sanitary District). This district runs from the Black Bear Casino in Cloquet up past the Lester River. The treatment plant is in the Lincoln Park area which has an arts district, fancy restaurants, and several breweries.

Most of the water comes with gravity down the hills of Duluth. Water from Cloquet has to be pumped up hill with augers. The water is strained with metal bars and a comb comes up and collects the baby wipes, menstrual products, condoms and other trash that gets taken to the landfill. The treatment plant does not want to offend their neighbors in Lincoln Park so the smelly air is pipes to this area. You can see the far ends of the pipe at the end of the wood chips. The pipes has holes so the smells are released under a six foot bed of wood chips that cleans the air. I could detect some odor but it wasn't nearly as bad as I expected.

Here is the lab where they can test the waste water. Bacteria does most of the cleaning so they must make sure the pH is suitable. They also test the cleaned water to make sure it meets standards before it returns to the St. Louis River. In the summer, when the river is being used recreationally, bleach is added to the water. In the winter the water is released without bleach.

This is the grit station. Sand, small pebbles and soil filter to the bottom and taken away. 

We all had to wear hard hats, safety glasses, and receivers with one head phone so we could hear our guide talking. This tour guide is a joker. Why was the toilet paper afraid to cross the road? The toilet paper was afraid it would get stuck in the crack.

I don't think you can see it but water is leaving the grit tank under this walkway.

In this tank they are piping in bubbles of ambient air to clear out the excess carbon dioxide.

This is where they store the solid wastes. For 12 to 14 days the water temperature is at 140 degrees to kill the viruses. For another 12 to 14 days the water temperature is kept around 100 degrees. By the end of this the product looks like manure. Farmers request that this get spread on their fields. To qualify for this product the farmer must have land that is mostly flat, not very sandy, and will grow grass or corn to be fed to animals. If, for example, a farmer wanted to fertilize his strawberries, he or she would have to wait eight years before harvesting the berries for human consumption. During this process, methane is removed. The methane is burned in heaters at the plant. Soon they will burn methane to create electricity. Electricity is the second most expensive thing here second only to labor costs. I really enjoyed this tour.