• ambient temperature
• neutral pH value and
• normal pressure

Characteristics of the Tholander biofiltration process in keywords

The decomposition of the pollutants takes place in a filter bed composed of organic, humidified material which is flowed through at low speed by the waste air to be treated. This filter material carrying a specific baterial flora grows at suitable environmental conditions and gradually adapts to the pollutants.

When flowing through the organic biofilter bed, the contaminants are being absorbed by the filter material and dissolved in a thin liquid film which is around the filter material. The now dissolved contaminants enter the cells of the microoganisms by means of diffusion and osmis and are decomposed into harmless products (cell material + CO₂ + H₂O). The biofilter's efficiency hereby depends to a special degree on the sorption capacity of the biofilter material as well as on the biological activity of its micro flora.

The properties and activity of the micro flora in turn are determined not only by material properties but also by the exhaust parameters. These include:

The biofilter's lifetime and efficiency can only be guaranteed under optimal exhaust parameters. This is why we adjust the pre-conditioning down to the smallest details to its specific application. This will save you negative experience e.g. with drying out, overwetting, ph change or aerosol deposition in the filter material.

The knowledge gained since the company foundation in 1980, has continuously been incorporated into the design of our biofilters. Based on this continuous improvement of our plant concept we could extend the advantages of biofiltration compared to other competing technologies such as chemical scrubbing, activated carbon adsorption or regenerative post-combustion.

Our biofilters are manufactured in modules made of glass fibre reinforced plastic (FRP) and can easily be assembled on site. This modular construction offers the possibility to displace or extend the plant at any time. In case of physically separated emission sources, the modules are set up individually as decentral air purification units.

Since the function of the biofilter is only as good as the pre-conditioning of its raw gas, a main focus of our innovation efforts is on the development of a reliable pre-treatment adaptable to any application. Our pre-conditioning unit is, in the simplest case, a humidifier with maximum efficiency. Extending it with dosing stations, multi-stage construction and setting of appropriate desalination rates, our pre-scrubber (cross-flow scrubber) also eliminates aerosols or pH-relevant air contaminants.

Biofilter materials differ in flow properties and biological activity. We have therefore various materials available which are chosen in such a way that an optimum pollutant reduction is achieved.

We adapt the concept of our biofilters to your specific application. Only custom-made plants guarantee customer satisfaction. This applies to:

• the equipment of the preconditioning unit
• the dimensioning of the biofilter
• the cover of the biofilter (both open and covered versions with chimney are possible)
• the option of driving access on the the grit floor
• the constructional adjustment to the installation site (e.g. roof installation, colour scheme, etc.)

Furthermore, our plants stand for a maximum of individuality with a minimum of efforts:

• delivery of turn-key solutions
• few preliminary works by the customer on site
• corrosion-resistant materials
• standardized and compact to transport components
• overseas delivery
• material-saving design
• colour scheme of the plant according to customer requirement
• savings regarding frost protection and ducting
• weather resistance
• driving access on the grit floor
• easy to use and maintenance friendly operation
• time-optimized installation on site
• supervised start-up with training for the operating staff
• sophisticated maintenance concept being already considered in the planning phase
• modifiable, retroffitable plants (e.g. in case of variable crude gas amounts)

The dimensioning of the plants is based on VDI guideline 3477 as well as on our long-time experience considering customer and application-specific requirements. But even in applications where there is either no experience with biofiltration yet or need for optimization, we will be pleased to work out a concept for you. In this case, pilot tests will be carried out with one of our pilot plants. This helps on the one hand to clarify whether it makes sense to use a biofilter in general and can reduce investment and operating costs due to an optimum design of the pre-conditioning on the other hand.

Biofilters are unbeatable in cleaning odorous or low concentrated exhaust air. We have more than 800 references in these areas. In addition to that, biofilters are also suitable for the removal of volatile organic compounds (VOC) where other methods would be profitless in economic and ecological terms.

• Waste water treatment
• Composting plants
• Waste treatment
• Food production
• Leather production
• Tobacco processing
• Fermentation
• Breweries
• Decomposition of solvents (VOC)