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Trickle filter and degassing unit media

Trickle filter degassing media can come in many different shapes and sizes.

A balance between design, packing configuration, water and gas mixing, surface area and void space is important to the overall performance of trickle filter media.

For biological filtration, trickle filter degassing media with a good void ratio with the highest possible surface area is desired to result in the best gas exchange, oxygenation and nitrification mix. Biological filters that use the trickle tower/trickle filter design simultaneously degas CO2, oxygenate water and convert ammonia to nitrite to nitrate.

For CO2 degassing, a high void space should be the main concern with media design to reduce waste buildup, maximise water flow and optimise gas movement.

In both applications air is commonly force counter current to the water flow to maximise the gas exchange inside the filter or degassing unit.

Degassing units are commonly applied following biological filters such as moving bed biofilters


Biological trickle filter media

Degassing Rings

High waste load degassing media

Do not dismiss the power and efficiency of a trickle filter.

As long as attention is paid to gas exchange inside the filter, and water distribution, the trickle filter is incredibly efficient as TAN removal and simultaneous degassing.

Degassing is very important in RAS systems for removal of CO2 and other dissolved gases, it is even more important when using submerged filters like Fluid bed sand filters and MBBR’s.

Trickle filters have a wide loading range in both water flow and TAN removal, as TAN levels increase so does TAN removal and so can be very well suited to shock loaded systems.

Trickle filter media can come in various shapes and sizes, commonly pinned bioballs or a variety of other carbonate based medias have been used.

Pure Aquatics’ Degassing Bio Balls have a higher surface area per m3 and feature a sufficient void space to allow for simultaneous degassing.

The bladed shape of the balls allows for sufficient shearing of biofilms that get too thick and help to prevent mulm build up by eliminating the small spaces often present in pinned bioball designs.

As with all biofilter designs, sufficient pre-filtration and removal of solid waste will improve removal rates.

For assistance with sizing and design of trickle filters please contact us and we would be happy to assess your application.

Degassing rings are an established design of degassing media with a high void space and gas exchange capability for the removal of dissolved gases in waste streams.

Degassing rings are often used where high flows and high solids loads are present. Due to their high Void space, open design and lower surface area, they are more resistant to blocking and therefore stay cleaner for longer. They also do not have as high of a pressure drop and therefore more air can be forced through them (either actively or passively) resulting in better gas exchange.

Predominantly used for degassing, with a small capacity for nitrification, degassing rings are a great option for dissolved gas removal where biological filtration is not the primary concern, or biological filtration is already adequately sized within the system.

Product Size (approx) SSA m2/m3 Void Space
Degassing Bio Balls 25mm 25mmD 460 84%
Degassing Bio Balls 38mm 38mmD 325


Degassing rings 25mm 25mm x 25mm 175 90%
Degassing rings 38mm 38mm x38mm 155 89%