The Red Oak wastewater plant is a Grade III trickling filter treatment facility. The plant is designed to treat an average dry weather flow of 1.2 million gallons / day (MGD), an average wet weather flow of 2.2 MGD, and a maximum flow of 4.9 MGD. The design biochemical oxygen demand (BOD) load is 1895 lbs. / day.

All waste water comes into a pump station where it goes through a bar screen to remove debris that is too big to go through the pumps. It is pumped to the grit removal system and then the water is divided between 2 primary clarifiers. Sludge settles and flows to a sludge thickener for further settling. Scum, which is made up mostly of household grease, floats to the top and is skimmed off and pumped to the digester.

Flow from the primary clarifiers is pumped to the trickling filter for removal of BOD. It then is pumped to the packed towers which aid in the removal of ammonia nitrogen. The water then flows to the 2 final clarifiers. Any sludge will settle and flow to the sludge thickener. The water that overflows the final clarifiers is then discharged to the East Nishnabotna River.