Biosolids and Headworks Improvements
O’Fallon, MO

Stainless Steel Odor Capture Hood

Horner & Shifrin prepared a facilities plan for improvements to the City of O’Fallon’s existing biosolids and headworks facilities. The firm subsequently prepared plans and specifications for these improvements which have been completed and officially began operation in the fall of 2000. The City previously used a converted package treatment system to gravity thicken and aerobically digest the biosolids generated at its wastewater treatment facility. For many years, biosolids generated at this facility have been pumped to a nearby lagoon for permanent storage. With the promulgation of the Part 503 regulations, the City undertook a plan to eliminate its current lagoon system as well as evaluate alternatives for producing either Class “A” or Class “B” biosolids.

The new biosolids facilities are capable of producing Class “A” biosolids through a combination of gravity belt thickening of the waste activated sludge, belt filter press dewatering of blended primary sludge and thickened waste activated sludge, and stabilization through the Envessel TM Pasteurization process of lime and heat addition. In addition, because the existing headworks facility was not effective in removing grit material from the biosolids end-product, a new screening and grit removal system was constructed as part of the project.

The plant includes the following major unit processes:
Two 2.0 meter belt filter presses
Two 2.0 meter gravity belt thickeners
One Class "A" Envessel Pasteurization System including Thermofeeder, Thermoblender, and Pasteurization Unit.
300,000 gallon sludge blend tank
Belt filter press feed pump station
Gravity belt thickener feed pump station
Process water pump station
Primary sludge pump station
Sludge blend tank aeration system
Sludge blend tank recirculation pump system
Waste activated sludge aeration system
Sludge processing, loading, and storage building
20 mgd influent screen system
20 mgd influent grit removal system

The City of O'Fallon is currently in the process of developing a market for the end-product as a soil amendment or a fertilizer under the trademark name "Nature's Blend".

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