KWS Manufacturing

Biosolids Cake Handling System for Storage and Truck Load Out at Waterloo, ON WWTP

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End User or Owner

City of Waterloo
Waterloo, ON

Consulting Engineer

AECOM
Markhan, ON

Contractor

Graham Construction
Mississauga, ON

Plant Name and Location

Waterloo WWTP
Waterloo, ON

General Description of the Application

The City of Waterloo in Ontario, Canada is a vibrant city with a growing population. The demands of the city required expansion to the Environmental facilities. Part of the expansion was adding new centrifuges and a Cake Handling System for dewatered biosolids. The Cake Handling System (CHS) received dewatered biosolids from one to three Westfalia centrifuges and delivered it to one or two Storage Bins. Storage for three days of dewatered biosolids production (200 tons) was required for operational flexibility (i.e. over holiday periods). Under each bin was a Live Bottom Feeder with a series of water-tight discharge gates. The Live Bottom Feeders and gates would then evenly load trucks for removal of the dewatered biosolids from the site.

A need to rapidly load trucks in a highly automated manner was required to minimize truck time on site and to limit the amount of manpower required from the plant staff.

The City of Waterloo contacted KWS because they needed a design partner who could work with the consulting engineer and mechanical contractor to develop a complete system that would achieve all the operational needs and then to manufacture and supply an integrated package with one point of responsibility.

Design Parameters of Application

ParameterDistributionConveyorsTruck LoadingLive BottomsBins
Volume – m3/hr:18 m3/hrup to 48 m3/hr110 tons each
Density:800-1000 kgs/m3800-1000 kgs/m3800-1000 kgs/m3
Dry Solids:25-32%25-32%25-32%

Advantages Provided by KWS

KWS designed, manufactured, supplied and commissioned an integrated system which required expertise in many different areas. KWS had previous experience and a complete understanding of the process conditions at the Waterloo plant. KWS then applied this experience and knowledge to the design and fabrication of screw conveyors, screw feeders, slide gates, chutes, and support structures. KWS also supplied application engineering of instrumentation, motion sensors, level sensors, overload protection, truck position sensors and the design of PLC based controls with touch screen OITs.

Special Features of KWS Design

Since one Distribution Conveyor distributed dewatered biosolids cake from one or all three centrifuges, it was essential that conveyor flexibility was maximized. The Distribution Conveyor was split with a drive at each end so cake could be distributed to either bin or both bins at the same time. The Distribution Conveyor was long in length and required intermediate bearings. KWS utilized the extra heavy KWS-WW intermediate bearings to achieve this objective.

Availability was further improved by using a PLC based control system with fault detection and dynamic path reconfiguration. In the event that a fault was detected, the system assessed whether an alterative path was available and reconfigured the Distribution Conveyor without interruption of the centrifuge operation.

Redundant, pneumatically actuated slide gates were used on the discharges of the Live Bottom Feeders. In the event that the system detected a gate failure to close, a second gate on the same discharge would close.

Trucks are guided into the truck bay using traffic lights which use proximity sensors. Level sensors are located adjacent each live bottom discharge and sense the height of cake in the truck. Slide Gates are opened and closed to provide an evenly distributed load of a certified weight into the trucks using information from the Bin Weigh System, Truck Scale and level sensor systems.

Testimonial

"KWS was an important partner from project development to final commissioning of the Cake Handling System."

German Nunes, Project Engineer – Waterloo WWTP Project, Black & Veatch

Biosolids / Sludge

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