My city had an open house of our Pflugerville Public Works Water Treatment Plant. I was mainly interested in how they clean our sewer water.
It looks like a classic system. It was designed and built in 1986. It has a inorganic, trash separation station. An aeration phase that pumps air into the water to activate the bacteria to eat the organic compounds. A clarifier phase to separate the heavy matter.
A chlorine phase to disinfect the water, before send to the creek. The slug that is removed in the clarifier is mixed with wood chips to create compost and is free to any city resident for pickup.