Wastewater Treatment Plant

Treatment Plant Aerial

The Idaho Falls Wastewater Treatment Plant is designed for 17 MGD, 35,000 lbs. BOD, and 38,000 lbs.TSS. It currently receives 9.2 MGD, 19,500 lbs. BOD, and 21,200 lbs. TSS.


Upon entering the plant, the wastewater passes through a pair of escalator punch plate screens. The raw sewage is screened using fine screening technology with an opening of approximately 6 millimeters.


The solids removed by fine screens are washed to remove organic material, dewatered and compacted to remove the free water, and loaded into a storage dumpster. All of the equipment and facilities are located indoors in the new Headworks Building to facilitate equipment operation and maintenance. The screened material is disposed at the County sanitary landfill.

Grit Chamber

The wastewater then flows to an aerated grit chamber.


The wastewater then flows to the primary clarifier. Floatables from the top of the clarifier and the settled sludge from the bottom are pumped to the primary digesters.


These digesters are an anaerobic type and utilize the mesophilic temperature range (approx. 98 F) for digestion and stabilization of sludge. These digesters produce Methane gas which is used for heating the digesters and support buildings.


After leaving the primary clarifier, the wastewater flows to the secondary pump station where it is pumped over an activated biological filter tower. The purpose of this tower is to remove nutrients and act as a buffer to prevent “shock loads” from affecting the activated sludge system.


This tower utilizes redwood media and the wastewater is passed over it at a super rate in excess of 27 million gallons a day.


Upon discharging from the tower, the wastewater enters the aeration basins. The basins are of a complete mix type and utilize floating aerators with propellers to provide aeration and mixing. These basins together with the “tower” provide an environment for higher bacterial life forms to develop. These bacteria multiply utilizing additional wastewater as a food source. Normal detention time for the basins is about five hours under present flow conditions.

secondary clarifier

Following aeration the flow passes to the secondary clarifiers providing a resting stage where the microbial solids “clump” together and settle.


The settled solids return (underflow) to the secondary pumps station and remixed with primary effluent thus creating activated sludge. A portion of this recirculated settled sludge is wasted daily to the solids handling building where gravity belt thickeners thicken the sludge and pump it into the primary digesters. It is wasted to keep the microbial population in balance.


After clarification, the wastewater (overflow) enters the chlorine contact chambers where it is disinfected with chlorine gas.  Following disinfection the residual chlorine is neutralized with sodium bisulfite and discharged to the Snake River.


Following anaerobic digestion, the sludge now known as Bio solids is further stabilized in a storage lagoon and easily meets all the “Class B” requirements set forth in the 40 CFR 503 regulations.


A dredge is used to pump the Bio Solids into tanker trucks.


The Bio Solids are used as a fertilizer and soil conditioner on farmland in the area.


The Wastewater Treatment Plant has a laboratory that tests for pollutants to determine the efficiency of the operation and the protection of the Snake River.