Complete Residuals Handling System for Stickney WWTP

General Description

Stickney Water Reclamation Plant in Chicago is owned by the Metropolitan Water Reclamation District (MWRD) and is the largest wastewater treatment plant in the world with a capacity of 1.44 billion gallons per day. It is located on 570 acres in Cicero, Illinois, southwest of Chicago, and serves 2.4 million people living in Chicago and 43 suburban communities. It consists of two plants — the western plant which began operating in 1930, and the southwestern plant which entered service in 1939. The Mainstream Pumping Station, the largest underground sewage pumping station in the world, lifts sewage from a deep tunnel system 300-feet underground to the plant. The sludge from the plant is dried and pelletized by Metropolitan Biosolids Management, a joint venture of Biosolids Management and Veolia Water North America Operating Services, which received a 20-year contract to design, build, own, operate and maintain the pelletization plant.

In 2005 as part of an upgrade at the Stickney WWTP, Primary Settling Facility, KWS provided a complete residuals handling system from the collection skimmers to storage at two dumpster bays. The KWS system consisted of Shafted Ribbon Screw Conveyors as detailed in the following table and including the features below:

The KWS equipment had the following features:

1. ¼-inch thick 316L SS double formed flange troughs per CEMA 350 standards
2. 1/8-inch thick 316L SS flanged covers with quick release hinges on one side and quick release over center clamps on the other.
3. 3/8-inch thick ribbon flighting mounted on a 3-inch schedule 80 pipe and complete with intermediate bearings.
4. Pipe ends with KWS standard Quick Key (QK) couplings.
5. 316L SS auxiliary supports including a special A-Frame that spanned existing facilities.
6. SAE 4140 drive and end shafts with wear sleeve and C-1045 intermediate shafts.
7. Three ring split housing packing gland seals with Teflon packing
8. Integral drive support complete with shaft mounted, AGMA Class II gear reducer, external drive end bearing.
9. V-belt drive motor complete with 316L SS guard.
10. Conveyor Components motion sensor switches.
11. Conveyor Components Model RS-2L emergency pull cords.
12. 316L SS chutes with neoprene flexible connections.
13. Loading Conveyor SC-4 was mounted on an automated center bearing to allow the conveyor to pivot through an arc of 120-degrees. SC-4 was complete with control switches to stop the swivel at any intermediate position manually during operation.

Design Parameters

KWS Advantages

The application at Stickney WWTP required a unique layout in order to fit the new KWS residuals handling system into an existing building to carry residuals through two separate buildings to a space-constrained loading area. Two loading bays were required but there was insufficient space or infrastructure to install two loading conveyors to distribute residuals into the dumpsters. The building classifications were Class 1, Division 1, an explosion-proof environment requiring instrumentation, motors and control panels to be designed and built for this environment. As a full capability manufacturer with extensive design resources, KWS designed and manufactured a system that met all the customer’s needs.

Special Features

Access to the equipment was limited so KWS Quick Key (QK) couplings were used to allow sections of screw to be installed and removed without disturbing adjacent screw sections. In the loading area, a single swivel conveyor was designed which could load either of the two bays and which was supported from the floor. The swivel conveyor can be rotated out of the way to change dumpsters. Due to limited headroom, the swivel conveyor was mounted closer to the top of the dumpsters. The swivel assembly consisted of a sealed bearing assembly mounted vertically between the support column flange and the conveyor flange.