Luggage Point Dewatering Project

Client: Queensland Urban Utilities

Technology: GE PACSystems RX3i & Citect SCADA

Witthoft Engineering was responsible for the design and implementation of the Power and Control of the Luggage Point Dewatering Project Upgrade, installing 3 new Alfa Laval Centrifuges with new Feed Pumps and Complete Poly Batching and MHL Dosing Systems.

The Power Design Included:

• Power System Analysis
• Switchboard Design
• Over 240 Drawings
• I/O Lists
• Cable Schedules
• Equipment Lists

The Control Systems aspect of the project included the code for 2 RX3i GE PLC’s, PLC to PLC Communication as well as MODBUS TCP Communication to:

• 3 Centrifuge PLC’s
• 16 Danfoss VSD Drives
• 17 TeSys DOL Drives
• 2 MOXA Switches
• 2 HMI’s
• Air Circuit Breaker (controlling opening and closing through HMI)
• 2 Power Meters
• Fire Alarm
• Harmonic Filter
• 2 UPS Units

The Dewatering PLC receives operator commands from SCADA and controls the Centrifuge based on sequence conditions. The three sludge Feed Pumps each supply the Centrifuges from a Storage Digester. To prevent the build up of Struvite in the Sludge Feed Lines, MHL is dosed into a Sludge Recirculation Pump back into the Storage Digester.

To aid the sludge thickening process, Polymer is batched, then diluted with water and dosed to the sludge as it is fed into the Centrifuges. The Centrifuges are fed by separate Polymer dosing pumps, each dedicated to a unit.

The dewatered sludge is conveyed to Sludge Bins via a common conveyor and a stacker/bin system. It is then loaded onto a truck and carted from site for reuse as a soil conditioner or for disposal. Centrate is collected at the Centrate Wet Well and pumped to the Supernatant Wet Well located at the Digester Complex.