KWS Manufacturing

Shafted Screw Conveyors for Conveying Dried Sludge Jones Island WWTP in Milwaukee, WI

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Jones Island WWTPEnd User or Owner

Milwaukee Metropolitan Sewerage District (MMSD)
Milwaukee, WI

Consulting Engineer

Black & Veatch
Milwaukee, WI


Marshall Erecting
Milwaukee, WI

Plant Name and Location

Milwaukee Metropolitan Sewerage District - Jones Island WWTP
Milwaukee, WI

General Description

The primary wastewater treatment plant at Jones Island in Milwaukee, WI was one of the first of its kind when the original activated sludge plant was constructed in 1925. The Milwaukee Metropolitan Sewerage District (MMSD) was the first to market biosolids created through this process as a fertilizer under the name “Milorganite.” Jones Island was the first wastewater treatment facility to economically dispose of the recovered sludge by producing an organic fertilizer. The 1925 plant has been designated as a Historic Civil Engineering Landmark by the American Society of Civil Engineers.

The heart of the MMSD Dewatering & Drying Facility is twelve rotary dryers for drying and pelletizing dewatered sludge to create pellets. The dried sludge is very abrasive equipment maintenance is a daily issue. As part of a continuous improvement process for the facility, the MMSD needed to replace the Main Recycle, Screw Conveyor #1 and Wet Recycle Screw Conveyors #1 & #2. These screw conveyors are highly specialized and unique conveyors that needed to be updated to new code requirements imposed by NFPA68, Explosion Protection using Deflagration Venting.

KWS Environmental has been providing screw conveyors, bucket elevators and associated equipment to the Jones Island site for over 20 years and fully understood the requirements of the Customer and the application. The MMSD needed a supplier like KWS Environmental with the engineering knowledge and manufacturing experience to help solve the unique problems of the application.

Design Parameters

  1. Type of Sludge: Dewatered and Dried Sludge
  2. Material Density: 45 to 55 Lbs. per Cubic Foot
  3. Solids, percent by weight: 80 to 97-percent
  4. Capacity (max): 100 Tons per Hour
  5. Capacity: 3,650 Cubic Feet per Hour
  6. Duty: 24 Hours per Day, 7 Days per Week

KWS Advantages

Jones Island WWTP

The screw conveyors were designed specifically for conveying dry, abrasive sludge and required close tolerances to match existing space constraints and to connect to existing inlets, discharges, foul air connections and support locations. KWS Environmental used its expertise and engineering resources to quickly and accurately generate 3D models of the equipment and areas of the plant for field verification of the design before manufacturing commenced.

Additionally, explosion and deflagration vents were designed and located on each screw conveyor at intervals defined by NPFA-68 without interference with existing building infrastructure.

The KWS Environmental equipment was installed by Marshall Erecting without even a minor issue, saving both time and money.

Special Features

Jones Island WWTP

The KWS Environmental screw conveyors were designed with a number of special features to meet the unique conditions associated with this application. The dried sludge conveyed is extremely abrasive. KWS Environmental provided screw sections with a weld-on chromium carbide hard surfacing material to infinitely extend operating life. Areas of the troughs under the inlets were lined with epoxy-bonded ceramic tiles to eliminate wear on the troughs as the abrasive dried sludge enters the screw conveyors.

The Main Recycle, Screw Conveyor #1 conveyor is over 160-feet in length with a relatively large number of screw segments and internal hanger bearings. Given the space constraints, the screw sections had to be removable without disturbing adjacent sections. KWS Environmental provided Quick Key (QK) couplings so screw sections could be removed without removing adjacent screw sections or shafts.

Explosion deflagration vents and flame arresters were provided to meet the requirements of NFPA68 for dusty, indoor environments. KWS Environmental worked directly with Black & Veatch to determine the size, quantity and location of each deflagration vent.


"Due to the large number of sub-assemblies required to meet our installation sequence requirements and the very short shut down time slots, we required a very high standard for design and manufacture. Everything fit up well and we got up and running ahead of schedule. We wouldn’t hesitate to use KWS again where high quality is essential!"

Joe Marshall, Owner – Marshall Erecting

Jones Island WWTPJones Island WWTP
Biosolids / Sludge

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