Difference Between Biofilters and Bioscrubbers

Introduction

Biofilters and Bioscrubbers are the two biotechnology systems that help in controlling air pollution and odor control. Here we use biological organisms for the removal of toxins as the harmful gases and odors caused by the activities of the industries and enterprises pose a great threat to human and environmental health.

How Biological Control Systems Take Out the Odor?

Typically, all the biological systems use naturally occurring bacteria that feed on odor-producing substances as a food choice. Some of the bacteria are listed below

• Acidophilus bacteria are primarily used for the removal of H₂S odor.

• Specific bacteria or fungus for the removal of VOCs and Ammonia.

Bacteria usually get nutrients from the organic matter which is used as a medium. When an inorganic medium is used for purification in the system, an external supply of nutrients for microbial growth is required.

All the biological systems must be provided with the following parameters

• Specific levels important for certain bacteria.

• Consistent foul air source, water, and media bed are needed.

• Temperature is usually maintained at 50-100F.

• All the purifying biological systems must require an extended period of 2 weeks for microbial colonization.

The two main biological control systems are Biofilters and Bioscrubbers.

Biofilters

These have organic substrates which allow the desired growth of bacteria. Here the air is percolated through this system.

Bioscrubber is a system with an inert substrate proving high surface area and is pumped with nutrients and water to promote bacterial growth.

Biofilters are simple biological systems that are provided with an inlet, blower that sends air into a humidifier to maintain the humid conditions within the system. Typically, the microbes in the biofilter system require high humidity levels. Once the air comes into the humidifier this blows to the bottom of the system which has air distribution channels covered with gravel. On top of this gravel is a filter media that is open.

How do the Biofilters Work?

• First foul odor gas is pumped into the humidifier through the duct.

• Bacteria use the filter medium as nutrients and grow on the medium forming a biofilm.

• The medium has a good water-holding capacity and soluble chemicals within the waste gas are dissolved into the moisture.

• These bacteria then oxidize the hydrogen sulfide present in the pumped air.

Bio Scrubber Systems

Bio scrubber systems purify the acidifying gases like H2S, VOC, amines, R-SH, Sox, NOx, etc. from the exhaust before entering the atmosphere to prevent the formation of acid rain. A packed bed scrubber also called a packed tower scrubber is designed mainly to remove both particulate matter as well as gaseous pollutants. Here the contaminated gas stream is fed into the tower which has a special packing material.

Nozzles present here spray the scrubbing liquid on top of the packing material and the liquid works its way down the tower. The spray nozzle is important to increase the wet area. Flow rates of the spray nozzles have been carefully monitored for the efficiency of reactions.

The gas passes up through the packing material. These packing materials increase the contact surface area between the exhaust gas and the bacteria. This increases the necessary time for biochemical reactions within the system. The particles and the gas molecules come in contact with the biofilm made up of the micro-organisms on the packing liquid.

The solution required for the feeding of bacteria should be able to be renewed and dosing is controlled while the system is still running. The contaminated liquid drains down through this packing material passed the packing support and outflows the bottom of the tower. The gas stream flows out through the top of the packing material pass the nozzles and through a mist eliminator before exuding the tower.

Differences Between Biofilters and Bioscrubbers

Biofilters

Biofilters are usually of low cost and can be placed in-ground or above the ground. These can be covered or uncovered. In biofilters, a porous organic medium is generally used which may include the following substances.

• Bark, wood chips.

• Coconut husks.

• Soil.

• Peat.

• Engineered glass products.

Air needs about 30 seconds time to get percolated through the filter medium. Biofilters are typically used for low foul odors and are of low maintenance. They are mainly used for H2S removal.

Bioscrubbers

Bioscrubbers use the following substances as their filter medium to increase the surface area.

• Lava rock

• Plastic material

• Polyester mesh

• Utherane foam

• Glass foam

Lava Rock

• Bioscrubbers are typically designed for the colonization of one type of bacteria and provide about 99% efficiency in the removal of H2S.

• This media requires low pH levels usually 1.5 to 3.

• Bacteria oxidize the hydrogen peroxide and produce elemental sulfur and sulfate as by-products.

• Constant water recirculation is necessary.

• Empty bed resident time of only about 10-15 seconds is needed which is less when compared to the biofilters.

• Bioscrubbers assures the removal of about 99% of the hydrogen peroxide in the provided foul air.

• These systems are more complicated but effective for the removal of high odor levels with medium maintenance.

• These are used for both ammonia and H₂S.

Conclusion

Bio scrubber is most efficient system for the removal of hydrogen peroxide when compared to the traditional biofilters. In bio scrubbers the pollutants are absorbed from the gas stream by the supplied water flow. These are then biodegraded by the micro-organisms.

This system is provided with purifying scrubbing liquid through the nozzles. The hydrocarbon is biodegraded by organisms and gets converted to water and carbon dioxide and the non-biodegradable substances remains in the water wash.

Biofilters are mainly used for the processing of waste water, capturing harmful chemicals and removal of pollutants from the air. This systems can reduce up to 95% of odor in the air. Biofilters need to be watered constantly to maintain optimum conditions.