Biofiltration for odours, sulphur compounds and VOCs

Biofilter

Biofiltration is a biological air treatment technique in which pollutants are degraded by microorganisms immobilised on an organic packing material. It is especially effective for odours, sulphur compounds and VOCs in large air flows with low inlet concentrations, provided that humidification, preconditioning and reactor sizing are properly controlled.

Why choose a Biofilter?

Odour removal

Removal of volatiles in relatively low concentrations (0.001 g/m³ to 1 g/m³):

toluene
aromatics (toluene, styrene,…)
alcohols (methanol, ethanol,…)
hydrocarbons (pentane, hexane,…)
others (aldehydes, esters, …)

Pollutants treated with biofiltration

Emission control system for acrylate, acetate and aldehyde vapours

Acrylates, acetates and aldehydes

Alcohols and ketones

Air treatment for ammonia and amine emissions

Ammonia and amines

Air treatment system for aromatic compound emissions

Aromatic compounds

EtO abatement system for ethylene oxide waste gas treatment

Ethylene oxide and other epoxides

Air treatment system for hydrocarbon emissions

Hydrocarbons

Air treatment system for H₂S, DMS, DMDS and other volatile sulphur compounds from bio‑industry emissions to reduce odour impact.

Hydrogen sulphide and volatile organic sulphur compounds

Odour

Trevi's biofilter build on a roof structure to ensure optimal use of space

How does Trevi's Biofilter work?

In a biofilter, the waste gas is blown through a reactor which is filled with an organic carrier material, as e.g. wood chips, bark or mixtures. During the start-up of the biofilter, the presence of pollutants in the waste gas will result in a shift from the natural microbial flora on the carrier material towards a predominance of the most suited groups of microorganisms that efficiently metabolise the target pollutants. Only in exceptional cases, inoculation with selected microorganisms is needed in order to minimize the start-up period.

Biofilter for odour removal and the removal of volatiles in relatively low concentrations

Dimensioning and air preconditioning

Crucial with regard to the biofilter is the correct dimensioning of the reactor in correspondence to the air flow/pollutant load and the correct preconditioning of the incoming air. Regarding the latter, a nearly 100% humidification of the incoming air is crucial. For some waste gases, a chemical scrubber is needed in front of the biofilter in order to remove too high concentrations of e.g. ammonia or hydrogen sulphide. For other applications, a peakshaver is advised before the biofilter in order to minimise a too strong fluctuation in pollutant concentrations.

Biofilter material and process stability

While the moisturised waste gas prevents the dry out of the biofilter material, the biofilter material serves as a carrier and as a source of missing nutrients for microorganisms. Depending on the composition of the waste gas, a pH-buffer (to counter acidification of the biofilter material) and/or slow-release nutrients can be mixed with the biofilter material to improve the long-term performance of the biofilter. In addition to this, an additional periodic dosing of nutrients using the surface irrigation of the biofilter material can be done.

Biofilter installed on a roof structure to ensure optimal space

Temperature range and cover options

Biofiltration is possible for waste gases with wet bulb temperatures till maximum 70°C. As a result of this, thermophilic biofiltration is possible for hot waste gases coming from e.g. food processing and rendering facilities (dryers, extruders,…) without the need to first cool down the gases. For some applications, the biofilter can be equipped with a cover/roof in order to collect the purified waste gas and send it to an adjacent stack or make it suitable for sampling of the purified gases.