BIONIK - Technologies for biological, physical and chemical exhaust air purification

BIONIK biofilters typically consist of a bed of bark or root wood chips covered with a layer of microbial cultures. A biofilter can only be used, however, if the harmful substances are water-soluble, biodegradable and non-toxic to micro-organisms.

The functioning of a biofilter is based on the principle of biological oxidation. The exhaust air is passed through the biofilter medium where it encounters the microbial cultures of bacteria and fungi. The microorganisms use the organic compounds in the exhaust air as a food source and convert them into carbon dioxide, water or other harmless compounds that are discharged together with the exhaust air.

Particular advantages of biofilters are their low energy requirements and sustainability. Unlike other exhaust air purification methods such as adsorption and thermal oxidation, biological oxidation produces neither waste heat nor pollutants. Biofilters are therefore an eco-friendly option that can help to reduce the carbon footprint.

Another advantage of biofilters is their flexibility. Biofilters can be used to remove a wide range of troublesome substances. After a certain start-up time, the microorganism population adapts by selection to the respective food supply – the pollutant to be removed.

Compared to other methods, the purification process has no need for chemicals or other additives. It is only necessary to ensure that the exhaust air is conditioned according to the needs of the microorganisms. In addition, biofilters are usually easy to install and reliable in operation, which lowers their cost compared to other exhaust air purification technologies.

The gas medium to be cleaned flows through the trickle bed while it is uniformly sprayed with a water/nutrient solution from above. The biologically active liquid trickles through the packed bed, is collected underneath the trickle bed and pumped back to the spray nozzles in a circuit. To maintain the quality of the scrubbing liquid, a partial mass flow is discharged as required and replaced by a new water/nutrient solution.

Compared to other biological air purification systems such as biofilters, a biotrickling filter has the advantage of being suitable for higher pollutant loads. Biotrickling filters are highly flexible and can adapt more quickly to pollutant loads and air volumes. They also require less space and can be accommodated within more compact plants.

In addition biotrickling filters have an advantage in reactions that lead to unwelcome reaction end products, such as salts and acids, as these can be discharged more easily from a biotrickling filter.

The scrubbing liquid may be water, diluted alkalis, acids or oxidising agents. A large contact surface between gas and liquid is required for good mass transfer, which can be created in the scrubber by droplet formation or by sprinkling the solid surfaces of a filler packing. Usually, a droplet separator is installed downstream of the scrubber stage.

Scrubbers are capable of removing a wide range of harmful substances and are therefore used in many different areas. Some typical applications are the cleaning of exhaust air from production processes containing pollutants such as organic and inorganic sulphur compounds as well as ammonia or amines.

The use of scrubbers reduces harmful emissions and minimises environmental pollution. In addition, they can help to save costs of exhaust air and waste gas purification by reducing the amount of pollutants for downstream waste gas purification technology in multi-stage processes.

In exhaust air and waste gas purification, activated carbon is used, for example, as an adsorbent to remove volatile organic compounds (VOCs) in the form of solvents, cleaning agents and petrol vapours, to break down hydrogen sulphide and sulphur dioxide and to remove odorous substances.

The special advantages of activated carbon are its high effectiveness and its versatility in removing a wide range of harmful substances. This technology is relatively easy to operate and requires little maintenance. In addition, activated carbon also works in combination with other technologies, delivering even greater purification effectiveness.

Another benefit of activated carbon technology is that it is environment-friendly and sustainable. Activated carbon is a renewable raw material and can be produced from a variety of organic materials. Furthermore, activated carbon filters can usually be reconditioned and reused, thus reducing the need to obtain new ones and minimising their environmental impact.