AS-H Belt Thickener

Using gravity to thicken dilute sludge and slurries, the Alfa Laval AS-H belt thickener is suitable for all municipal or industrial flocculated sludges – particularly those from biological and activated sludge processes. Low energy and polymer consumption and trouble-free operation give important reductions in both cost and hassle for wastewater management.

Alfa Laval Ashbrook gravity belt thickener

Numerous advantages for flocculation sludge thickening and dewatering

  • Reduce the volume of sludge, thereby reducing waste disposal cost
  • Low energy use and polymer consumption
  • Lower labour cost and cost of change, thanks to minimal need for operator attention and maintenance
  • Totally-enclosed, low-odour unit with easy access for better safety and work environment
  • Robust design avoids fatigue and wearing
Designed for high throughput rates and high product solids content, the Alfa Laval AS-H belt thickener is considered the industry standard for removal of liquid from a solid-liquid suspension/sludge. With a simple design the sludge thickener has a small footprint and is suitable for both indoor and outdoor installation in your effluent treatment plant.

How does the gravity belt thickener work?

The sludge thickener works on the principle of separating liquid from solids by gravity drainage through a slowly rolling belt cloth. It uses a sludge polymer mixing valve with an adjustable lever arm to ensure sufficient turbulent sludge/polymer mixing.

After this, the ramp feeding section delivers a consistent load across the filtration area to maximize filtration properties.

A sludge retention tank, also known as the flocculation chamber, is filled from the bottom and then rises up over a weir to ensure even distribution onto the belt. Sludge ploughs force the sludge into lanes, which allows free water to run through the belt cloth where sludge is not present, thus enhancing the pre-dewatering process. Sludge ploughs can be lifted to allow for removal of rags etc.

The result is excellent thickening in a totally-enclosed, low-odour unit.  


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