Bribie Island sludge management facility gets an upgrade

Hydroflux Huber recently completed an upgrade of the Bribie Island sewage treatment plant’s entire sludge management facility. A key part of the upgrade involved installing HUBER Q-PRESS Rotary Screw Presses to replace the old belt press technology.

The HUBER Q-PRESS Rotary Screw Press is a sludge dewatering system using for mechanically dewatering sludge produced from wastewater treatment. Suitable for use on municipal and industrial sludge streams, it includes the following features:

• A screw drive rotating the auger at 0.2–1 rpm.
• A sludge feed connection.
• A filtrate discharge connection.
• An auger with increasing shaft diameter and decreasing gap between flights.
• A screen basket with different spacing.
• A sludge cake discharge chute.
• Pneumatic cylinders for maintaining a continuously adjustable pressure of the discharge cone.

The volume between basket, shaft and flights continuously decreases, and the pressure thus increases, as the sludge is moved through the basket. The auger pushes the increasingly thicker sludge towards the annular clearance, defined by a circular opening and an adjustable discharge cone therein. The cone is pressed against the opening by pneumatic cylinders, thus maintaining a defined sludge pressure at the discharge end. A brush on the flights cleans the rotating screen from the inside and a motorised rotating spray bar backwashes it periodically from the outside.

Cake is discharged through the cone and filtrate collects within the main case and is discharged via gravity to the filtrate outlet flange. The feed to the Q-PRESS can be run under slight pressure (up to 500 mBar), which provides additional dewatering capability. The feed pump is to be provided with a VSD. In addition, the screw speed can be automatically adjusted based on the inlet pressure.

At Bribie Island, Hydroflux Huber managed the process, mechanical, electrical and civil design as well as the site installation works, site testing, performance testing and training. The upgrade also included ancillary services such as the control system and SCADA integration, polyelectrolyte batching and dosing, and solids transfer.

Luis Bastos, director of Hydroflux Huber, said there were a number of reasons why HUBER screw presses were chosen for the upgrade of the sewage treatment plant.

“First, disposing of sludge is expensive in terms of transport so reducing the amount of sludge helps drive down costs,” he said.

“Second, HUBER technology is very slow speed — the average is 0.5 rpm — so it is very low in energy demand and, because of the low screw speed, it is high in operational reliability with virtually no maintenance.

“Third, it sits within a compact and fully enclosed system so it is WHS-compliant.

“Fourth, it has very low operational costs and it requires minimal operator attention.”

Performance testing demonstrated significantly higher performance than the existing belt press, with cake solids in excess of 18% dry solids. The capture rate was consistently 95% or better, as Hydroflux Huber equipment is sized to achieve high capture without the need for secondary filtration. This was achieved even though the feed solids was generally only between 6000 and 8000 mg/L.

“While there are over 1200 of these unique sludge dewatering machines being used in many applications worldwide. The installation at Bribie Island is the latest in Australia, which is evidence of their outstanding performance in local conditions,” said John Koumoukelis, director of global business development at Hydroflux.

“The latest generation of these screw presses — the HUBER Q-PRESS — is proving very popular in both the Australian and international markets. This is because not only does it reduce sludge volumes and disposal costs by up to 80%, but also because it is more efficient and can be operated at even higher solids throughputs than older technologies such as belt presses.

“Our customers are choosing these over centrifuges because of their performance — with the lowest energy demand compared with centrifuges, we spin at 0.5 rpm compared with 3000 rpm of centrifuges — and significantly less maintenance compared with centrifuges.

“When you add in the fact of complete stainless steel fabrication, it is little wonder that in our view these are the best screw presses in the Australian market.”