Biofilter media to remove odour causing compounds from waste gas streams

Abstract

A biofilter media has one or more of a set of desired physical characteristics. The set of physical characteristics includes a sphericity of 0.75 to 1, a particle size of 1 to 16 or 4 to 8 mm, a uniformity coefficient of 2 or less and a surface area of 800 to 2000 m 2 /m 3 of media. The media is coated, supports microorganisms and is used to treat a waste gas stream.

We claim: 
     
         1 . A biofilter media comprising a core and a coating wherein the media or its core have as sphericity of 0.75 to 1 and a particle size of 1 to 16 mm. 
     
     
         2 . The media of  claim 1  wherein the media or core has a particle size of 4-8 mm. 
     
     
         3 . The media of  claim 2  wherein the media or core has a sphericity of 0.8 to 1. 
     
     
         4 . The media of  claim 3  wherein the media or core has a surface area of 800 to 2000 m2 per m3. 
     
     
         5 . The media of  claim 4  wherein the media or core has a surface area of 1000 to 1500 m2/m3 of media. 
     
     
         6 . The media of  claim 5  wherein the core is an expanded glass particle. 
     
     
         7 . The media of  claim 1  wherein 80% or more or 90% or more of the media or core are retained between square grid sieves having openings differing in width by 4 mm or less. 
     
     
         8 . The media of  claim 7  wherein one sieve has 4 mm openings and the other sieve has 8 mm openings. 
     
     
         9 . The media of  claim 1  wherein the media has a uniformity coefficient of between 1 and 2. 
     
     
         10 . The media of  claim 9  wherein the media has a uniformity coefficient of between 1 and 1.5. 
     
     
         11 . The media of  claim 1  wherein the coating comprises a bonding agent, an adsorptive agent and nutrients for the microorganisms. 
     
     
         12 . The media of  claim 6  wherein the expanded glass comprises silica and at least one alkali oxide. 
     
     
         13 . A biofilter having a housing, an inlet, an outlet and a media in a flow path between the inlet and outlet, the media comprising a core and a coating wherein the media or its core have as sphericity of 0.75 to 1 and a particle size of 1 to 16 mm. 
     
     
         14 . The media of  claim 1  wherein the media or core has a particle size of 4-8 mm.