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Biologic exhaust air purification plants gain more and more in importance for the different tasks of the exhaust air treatment.

Applied are three biological process technologies:

  • Bio scrubber
  • Bio filter
  • Trickle-bed scrubbers (also called bio-trickling filter)

This special importance of the biological procedures was achieved in the recent past, because they do not produce secondary emissions, as e.g. thermal exhaust treatment systems, which release additional combustion exhaust gases during auxiliary heating and with this generate so-called secondary emissions. These emissions are – among others – the climate-relevant greenhouse gases carbon dioxide (CO2,) and toxic exhausts as carbon monoxide (CO) and nitrogen oxides (NOx).

Wessel has disposal of broad practical know-how in biological systems for all three treatments with more than 500 installed biological systems.

Which of the three procedures has got the best fitness and the best forthcoming technique is – among others - depending on:

  • Composition of the crude gas
  • Concentration of harmful and odorous substances to be separated
  • Physiochemical properties of the contented substances, e.g. water solubility
  • Further exhaust gas ingredients, e.g. dusts
  • Exhaust gas temperature
  • Available space

The above-mentioned, generally known biological exhaust air cleaning systems had steadily been developed further and optimized by us for decades.

Special bio filter systems and bio scrubber systems had been developed, in order to reach an especially effective separation performance with likewise lower operational costs than traditional biological exhaust gas cleaning procedures:

  • Wessel-BIOCAT filter
  • Wessel-BIOCAT scrubber

With the particularly low specific operational costs these systems had been installed in most different industrial sectors meanwhile, and they more and more replaced the conventional biological systems.
The essential characteristics and low operational costs lead to the fact that these systems today are increasingly used for applications, where it deals with the cleaning of huge exhaust gas volume flows of several thousand up to several hundred thousand cubic metres of hourly to clean exhaust air.



Biological air treatment with BIOCAT-Scrubber is for various companies and communes an economic and efficient solution to achieve clean air values of the TA Luft and 31.BImSch (Country-specific General Regulations of the Authorities)

Our BIOCAT-scrubbers enable an exhaust gas treatment without filter and with this a waste-free resp. sustainable exhaust gas cleaning. The advantage: scrubbers can - in contrast to filtering separators - also be used in case of sticky and adhesive substances in the exhaust air as well for exhaust gases with higher temperatures.

For the different tasks from several industries Wessel offers more than 50 different types of scrubbers of most different scrubber systems:

  • Biological scrubbers
  • Chemische scrubbers
  • Dedusting scrubbers

Our particular scrubber systems are field-proven for more than 50 years and have been developed further continuously. On top of the present scrubber-development is - amongst others - the BIOCAT-scrubber. Here the washing water is continuously regenerated in a circulating water treatment and partly used in a close circuit.
Pollutants are eliminated sustainable and with the use of special microorganisms in the washing water. With our scrubber system combinations gaseous pollutants and dusts can be removed from the exhaust air. For this purpose Wessel uses the BIOCAT-DUO scrubber, with separated circuits for the washing water. We refer to most sustainable exhaust air washing, as separated dusts are often used in the process or are recycled energetically. Different from most thermal exhaust air cleaning systems, the biological exhaust gas cleaning preserves resources, i.e. it is free of secondary emissions, which are relevant to the climate and harmful, such as:

  • Carbon Dioxide
  • CO2
  • Nitrogen Oxides
  • NOx
  • Carbon Monoxide


  • No additional discharge of secondary emissions (CO2, SO2, NOx, Dioxins, etc.
  • High-efficiency in removing odours and harmful substances
  • High plant availability and high level of operational reliability
  • Safe compliance with regulations regarding clean air values
  • Low maintenance costs and minimal operating expenditure
  • Low energy costs, e.g. by heat recovery, with this low operational costs
  • Low required space
  • Modular and therefore multi-sided applicable concept
  • Adapted construction
  • Insignificant low biomass production
  • No-waste heat
  • No exchange of bio filter material, as required for bio filters
  • Good controllability of the system, also at presence of acid or basic matters in the exhaust air to be cleaned


The BIOCAT-Filter

Biological air treatment is for various companies and municipalities an economic and efficient solution to reduce odours, hazardous substances and solvents in the exhaust air. BIOCAT-Filters have proved to be of value in various application areas for many years.


  • High-efficiency in removing odours
  • Effective separation of dusts and aerosols
  • High level of operational reliability and plant availability
  • Low operating costs, e.g. due to low pressure losses in the entire plant
  • Low investment costs, because of a compact and space-saving construction
  • No discharge of secondary emissions (NOx, SO2, dioxins etc.)
  • The modular construction of the system, the plant can be adapted to changed input parameters step-by-step
  • Separate activation and deactivation of the individual BIOCAT-Filter segments for maintenance works
  • Also suitable for the established hall construction type
  • Secure observance of separation efficiency with the down-flow principle, which optimizes the moisture balance in the bio filter material


Trickle-bed Scrubbers

These systems are preferred for use with small exhaust air volumes and exactly defined exhaust air composition with low concentrations and low deviations in the concentrations. Because of these limitations in application and due to procedural reasons these systems are less common.

Do you have any questions on biologic exhaust air purification plants? If you have any further questions, please do not hesitate to contact us! We look forward to hearing from you: info(at)wessel-umwelttechnik.de

Information about BIOCAT-Scrubber (1,4 MB)

Information about BIOCAT-DUO-Scrubber (2,9 MB)