These are pictures of the cryogenic plant at PWD. The vertical towers are used for converting air to pure oxygen, which is then pumped through the wastewater. Pumping pure oxygen combined with the regular air “blowers” makes Philadelphia’s water one of the best in the world. Not all wastewater treatment plants do this.
The horizontal tanks are used for storing liquid oxygen. This is very beneficial for the plant because the liquid oxygen can be converted to a gaseous form if something ever cut off the oxygen in the plant, so it is a great back up.
It’s very loud over at the cryo plant with all of the tanks running, and every 10 minutes there is a loud sound resulting from the release of Nitrogen. The Nitrogen comes from the tanks that convert the air to pure oxygen. It is really cool to learn about this process, since some treatment plants do not have this. It’s also great to know that the quality of water in my city is very good and that it will most likely remain that way!