SCREW PRESS

The Alfa Laval Screw Press 40 is the solution for simple, costefficient dewatering of flocculated sludge without previous thickening to reduce sludge volume, and to lower transportation
and disposal costs. With a dewatering capacity up to 10 m3/h digested sludge or 20 m3/h waste activated sludge, it is ideal for midsize municipal and industrial wastewater treatment
plants that require a solution with minimal supervision, low power, noise and vibration levels.

The high-performance screw press is very user-friendly, reliable and robust with high uptime. Screw Press 40 is designed for minimal maintenance, and is characterized by several
innovative design features that keep installation costs and total cost of ownership down.

The moderate rotational speed and low power consumption of the screw press have a direct positive impact on operational costs. Another advantage of the moderate rotational
speed is the fact that the screw press has extremely low noise and vibration levels, which in turn is a benefit to the working environment. Alfa Laval controls ensure that the need for supervision is minimal.

Applications:
• Municipal wastewater plant sludges – primary, secondary, mixed or digested sludge
• Industrial slurries from e.g. food or chemicals production
• Biogas residue.

Design:
The drum is mounted in a casing where the screw conveyor is fixed at either end in strong bearings. The screw conveyor is powered by an electric motor through a geared transmission
to produce the slow rotational speed needed for optimal performance. The entire drum is totally enclosed and provided with inspection hatches for maximum operability and maintainability..

Design features of the Alfa Laval Screw Press 40:
The heart of the screw press, the drum, is mounted in a casing where the screw conveyor is fixed at either end in strong bearings. The screw conveyor is powered by an electric motor through a geared transmission to produce the slow rotational speed needed for optimal performance. The entire drum is totally enclosed and equipped with inspection hatches for maximum operability and maintainability.
A unique, patent pending frame with a special lattice grid structure ensures a very high structural strength with much less steel than a traditional screw press design. The light, planetary
gearbox enables a very high torque with low power consumption. Thanks to its low weight, the Screw Press 40 does not require a costly reinforced foundation. The wedge wire screens are split vertically, enabling easy on-site maintenance of the conveyor from the side, while it is still mounted in the casing. If necessary, the conveyor can be removed from the side and put back, eliminating the need to send the entire screw press away for service. This provides better access than traditional design, and keep downtime to a minimum.

Working principle
Dewatering takes place in an inclined drum with a wedge wire screen forming the cylinder wall, and an internal screw conveyor. Polymer is dosed and mixed in the dedicated Alfa Laval Polymer
Mixing Valve. The flocculated sludge suspension is then led into the screw press’ inlet and to the first drum section for drainage of free water. Gradually, the sludge suspension increases in dry
solids content as it enters into the pressure zone of the drum. By virtue of the counter-pressure created by a restricted outlet, more free water is released from the sludge cake as it progresses
towards the outlet. The released water is drained off to the reject-water (filtrate) outlet under the feed inlet.

Benefits:
• Easy to install due to its light weight
• Easy to operate with Alfa Laval controls
• Continuous operation with high uptime
• Cleaning of screens with screw press in   operation
• Extremely low energy consumption and noise   level
• Totally enclosed
• No additional flocculator tank and mixer   required as polymer mixing valve is included
• Optimized polymer effectiveness and   minimized consumption
• Easy maintenance due to high accessibility
• Low spare parts consumption