Air biofiltration and odour control in wastewater treatment plants: what to choose and why
In industrial wastewater treatment plants, odour control in a treatment plant mainly concerns volatile organic compounds (VOCs), with traces of H₂S and NH₃. Odours primarily originate from emissions of organic substances (amines, mercaptans, etc.) during the most exposed stages of the treatment process, such as preliminary treatment, pumping stations, and sludge handling lines, where gases and reduced compounds can be released.
To capture and treat this odorous air, the three most widely used air treatment technologies are: biofilters (biological degradation on a filter bed), scrubbers (wet washing with conditioning and chemical reagents), and activated carbon filters (adsorption). Biofilters are generally less suitable when dealing with poorly biodegradable compounds or high concentrations of substances that are toxic to the biomass.
In IDRO Group's AERNET Biofilters, the air is first conditioned in a pre-wash scrubber to remove coarse contaminants and stabilise humidity, then distributed evenly across the filter bed through an expansion chamber and perforated flooring with modular elements, helping to reduce preferential airflow paths and maintain more consistent performance.
If you would like to evaluate the most suitable solution for your plant, contact us: we can support you from emission analysis through to system sizing.
Biofilters for air treatment: BIOPOR and BIOMAT, contaminants, maintenance, and limitations
The integration of a biofilter for air treatment is particularly suitable for large airflow rates and “diluted” pollutant concentrations, which are typical of many wastewater and sludge treatment processes. In IDRO systems, the biological bed can be constructed using different filter media, and air biofiltration is sized according to airflow rate, air composition, and the continuity of the odour load.
- BIOPOR is an inert, porous granular material with a neutral matrix derived from expanded magmatic rocks, used as a filtering medium in biofilters and bioscrubbers. It is characterised by high porosity and low pressure drop, even under conditions of significant bacterial growth, with good resistance to temperature and humidity and an absorptive effect on ammonia compounds. Under “normal” operating loads, its declared service life is more than 15 years, reducing the need for periodic replacement.
- BIOMAT is a plant-based medium with a woody structure and medium particle size, biologically activated using IDRO’s proprietary bacterial blend. It is designed to maintain porosity and resistance to bacterial attack even under high temperature and humidity conditions and is less sensitive to interruptions in operation. However, it requires periodic replacement, with a typical lifespan of approximately 2–3 years depending on the load. In both cases, performance depends on irrigation, drainage, and proper air distribution, as channelling and bed dehydration are among the most common causes of reduced efficiency.
Scrubber and biofilter: when integration is worthwhile and how it works
A scrubber is often preferred when it is necessary to treat soluble or inorganic compounds, or when the incoming air stream is highly variable. Wet scrubbing allows air conditioning and, where necessary, neutralisation through chemical reagents.
For this reason, the scrubber + biofilter configuration is common, with the scrubber stabilising conditions (humidity and coarse cleaning) and the biofilter completing the biological degradation process.
A practical example of scrubber + biofilter integration among IDRO’s references is the Battipaglia (SA) composting plant for Fisia S.p.A.. Odorous air from the municipal solid waste buildings is first treated by vertical washing scrubbers, then directed to two deodorisation biofilters with effective surface areas of 2,380 m² and 900 m².
In this configuration, the scrubber helps condition the airflow and stabilise operation of the biological bed, which is filled with BIOMAT filter media and equipped with irrigation and drainage systems. The treated airflow rates are 238,000 m³/h and 90,000 m³/h respectively for the two filters.
Activated carbon filters for deodorisation treatment: when they are worthwhile and how to avoid unrealistic expectations
Activated carbon filters for deodorisation treatment operate through adsorption and are useful when compact, quick-to-install solutions are required, particularly for “polishing” residual emissions. They are especially suitable for relatively low airflow rates or as a final treatment stage after other processes.
Their main limitation is media saturation, making accurate load estimations and a replacement or regeneration plan essential. In the presence of peak loads or highly variable gas mixtures, a multi-barrier approach is often more effective, such as scrubber + biofilter systems or an activated carbon scrubber used as a final polishing stage.
If you are evaluating the best option among air biofiltration, scrubbers, and activated carbon for an industrial wastewater treatment plant, we at IDRO Group can support you with emission characterisation, system sizing, and selection of the most suitable solution, all the way through to turnkey installation and scheduled maintenance.
