Little Pigeon River - Overview and Details Of Sewer Plant Operation
By John Disque
Rainwater, melted snow, sink, tub, toilet water, etc flows through an underground sewer system to a treatment plant. The plant removes the pollutants and the water is released into a lake or river.
Step By Step:
The underground sewer network feeds into a regional intersector, a lot like a highway's system that leads all traffic to the same place: the treatment plant.
The process starts at the plant's pumping system, which is well below ground level. The wastewater collects in huge underground wells. At this point, the water contains huge levels of phosphorous (a poisonous element in the nitrogen family and harmful to waterways because it promotes the growth of algae.) Algae is usually green and settles at the top of waterways. This green mass is known as "blooms" and these blooms are toxic.
The contaminated water gets pumped to the surface level of the plant. From there it flows down discharge channels leading to the treatment building. At this point it is sprayed with chemicals that transforms the phosphorous in the water from liquid to solid so it can be removed later.
At the treatment building the water flows through screens that removes any solids larger than 2.5 centimeters (stones, paper, plastic, etc). Huge presses compact these solids squeezing out the excess water. The solids are then shipped off to a landfill where it's buried.
The water continues on its journey and flows into large tanks. I believe it was at this point in the process that the Gatlinburg sewer plant ran into trouble.
Very small particles in the water gradually settle to the bottom of the tank. Then they are removed and taken to the landfill.
To remove the remaining phosporous they add a chemical compound. This chemical compound completes the process and binds any remaining particles forming what are called "flocks" which are masses of phosphorous that look like snow flakes. Being these flocks are heavier than water they sink to the bottom in about 2 hours and form what's basically called "sludge."
A system of rakes and pumps collects the sludge and transfers it to the sludge treatment building. At that point it's tested to see if it needs to be treated further.
From here all the wastewater has been treated and flows into a system called "the outflow" (a series of channels that discharge the water into the river).
The sludge is again treated so that the filtering process can easily squeeze out the remaining water. Most of the sludge goes into incinerators to be burned. The ashes go to the landfill and some are transferred into pellets and sold as fertilizer.
The average phosphorous removal for any plant is about 75%.
Right now the question is: How much phosphorous is going into the Little Pigeon River?
Gatlinburg Sewer Treatment Plant Collapses
Published April 6, 2011
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