KWS Manufacturing

Mixing Dried Biosolids with De-Dusting Agent for Efficient Load Out The North Shore Sanitary District

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End User or Owner

North Shore Sanitary District - ZionGurnee, IL

Consulting Engineer

Independent Mechanical
Chicago, IL


Veolia Water
Milwaukee, WI

Plant Name and Location

North Shore Sanitary District
Zion, IL

General Description

The North Shore Sanitary District provides wastewater treatment for the eastern part of Lake County, Illinois. The District serves over 300,000 residents within its service area. The District owns and operates three advanced sewage treatment plants with a combined average design capacity of 63.4 million gallons a day and over 125 miles of interceptor sewers. The local collector sewers within incorporated areas of the District’s service area are owned by the local municipality. The sanitary and stormwater sewers within the District’s service area are separate systems; therefore, there are no combined sewer systems. The solids produced by the wastewater treatment processes are treated and disposed of separately.

Wastewater treatment requires an intricate balance of physical, biological, and chemical processes. Solids handling involves the treatment of biosolids removed from the wastewater treatment processes. The solids that are removed during the wastewater treatment processes still contain a large amount of water so to reduce the volume of solids and disposal costs, the solids are thickened and then dewatered by belt filter presses. The dewatered biosolids are then loaded into trailers and transported to the Zion Sludge Recycling Facility for drying prior to disposal. After the biosolids are dried, they must be transported to a truck load-out station for disposal. The dried biosolids contain a large amount of fines and are very dusty. Transporting the dry, dusty biosolids is a major problem so a continuous mixer was added to the process to mix a liquid de-dusting agent with the dry biosolids to significantly reduce the fines and dust. KWS and Veolia worked together to develop a solution. KWS designed and manufactured a single-screw Continuous Mixer fit for the application.

Design Parameters

  1. Material: Dried Biosolids
  2. Solids Content: 95-percent by weight
  3. Material Density: 37.5-Lbs. per Cubic Foot
  4. Maximum Design Capacity: 265 to 3,500 Cubic Feet per Hour
  5. Operating Temperature: 100 to 175-Degrees F
  6. Operating Pressure: 1-psig Internal Pressure
  7. Duty: 24 Hours per Day, 7 Days per Week

KWS Advantages

KWS had worked with Veolia Water on previous projects at the Stickney WWTP to provide Continuous Mixers for a very similar application. The Stickney project was a huge success for both Veolia Water and KWS, so Veolia Water contacted KWS for the Zion project. KWS custom designed the Continuous Mixer to match the space available and to connect to upstream equipment while ensuring that the mixing process requirements were achieved. Using 3D design software, KWS provided a workable design that was fully compatible with the layout requirements in a relatively short period of time. Our extensive experience with mixing applications including our proprietary performance modelling algorithms allowed KWS to verify that the design would achieve the mixing requirements.

Special Features

KWS provided a Continuous Mixer with many design features to maximize flexibility so the desired mixing blend could be achieved. The pitch of the mixing paddles were easily and infinitely adjustable. The mixer speed was also infinitely adjustable and controlled by a variable frequency drive (VFD). Given the abrasive nature of the bulk material, KWS provided chromium carbide hard surfaced paddles to extend operating life.

The mixing paddles are easily removable and replaceable. KWS also designed the Continuous Mixer with a high-torque drive unit to handle any upset conditions or changes in the process. The result was a robust, efficient and flexible mixer that will meet the North Shore Sanitary District’s needs for many years to come.


"We have worked with KWS in the past including a few projects that required mixers and have been satisfied with all aspects of their project delivery, including site support."

David Swarthout, Operations Manager – Veolia Water

Biosolids / Sludge

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