About AST

Bead Filter Basics

Bead Filters were first developed in Louisiana State University’s Civil & Environmental Aquatic Systems Laboratory in the early 1990’s by Dr. Ron Malone. Bead Filters are generally classified as “expandable granular biofilters” or EGB’s and are distinguished from other filters by the use of plastic floating granular filter media. Water from the aquatic system passes through the packed bed of plastic beads. The beads capture the solids, while simultaneously providing a large surface area (400 ft2 /ft3 ) for the attachment of nitrifying bacteria which remove dissolved nitrogenous wastes. Bead Filters are often referred to as Bioclarifiers for their ability to perform both biofiltration and clarification in a single unit.

Better Than Sand

Bead Filters were originally invented to overcome some of the major problems with using sand filters. Compared to sand filters, bead filters are immune to biofouling, they never require replacement of the bead media, they minimize water loss/usage, and reduce energy cost by lowering pump head requirements.

In fact, compared to high rate sand filters, bead filters comply with three of the major sustainability issues summarized in the LEED Green Building Rating System. Bead Filters operated with water pumps typically operate at low pressure (horsepower requirements, as well as energy consumption). Bead filters specifically designed to use airlift pumps for circulation operate with less than one psi headloss. Additionally, backwash water loss rates for Propeller Bead® Filters are as low as 10% and PolyGeyser® Bead Filters are as low as 1% of those experienced by typical sand filters.

Bead Filters are also easily automated, never require replacement of the filter media and are immune to caking and channeling when backwashed regularly.