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Bio-trickling filters and bioscrubbers are highly specialised odour treatment methods. They work by filtering odorous air through microorganisms and need to be properly designed for your business by a suitably qualified person.
Bio-trickling filters generally combine properties of both biofilters and bioscrubbers in that they contain media, water, and odour treating microorganisms. Unlike biofilters, they are smaller, enclosed systems that usually contain inorganic media that doesn’t need changing. The microorganisms grow within the bio-trickling filter media.
Bioscrubbers are much like bio-trickling filters, being smaller, enclosed biological filtration odour treatment systems. However, unlike bio-trickling filters, the microorganisms are grown in a separate reservoir and circulated/recirculated through the media.
Type of control
When you would use this
These filters work best on large volumes of low/consistently concentrated odour sources; however, they can be more difficult and expensive to install than a biofilter. The decision to use a biological filtration method, or the specific one for your site, is best done with a suitably qualified person. For assistance in choosing a suitably qualified person, see EPA’s information about engaging consultants.
Suitable for: various volatile odorous compounds from hydrocarbons like styrene or fatty acids, to sulphur or chlorine-laden compounds, or nitrogenous compounds such as ammonia.
Industries that would use this: bio-trickling filters and bioscrubbers are most commonly seen in industries that produce acidic gases, or water purification plants and animal holding/processing facilities, as well as the textile and tobacco industries.
Details and considerations
Similar to biofilters, bio-trickling filters and bioscrubbers are living odour controls that require correct conditions to maintain optimum odour treatment:
- Both of these filters require continuous operation to work best. Sites operating for less than 8 hours a day, 5 days a week, should explore other odour treatment options.
- The media within bio-trickling filters and bioscrubbers is usually made of a synthetic foam or plastic packaging variant, rarely needing, or ever requiring, replacing.
- Bio-trickling filters and bioscrubbers can support a wider variety of microorganisms than biofilters, meaning that they can be effective on a broader array of odours.
- Bio-trickling filters and bioscrubbers are often very energy efficient once installed.
- Bio-trickling filters need continuous monitoring of acidity/alkalinity (pH) and temperature within the filter. Temperature should be kept between 15°C and 45°C with optimum temperature between 30°C and 35°C.
- The pH within the filter can be adjusted or managed by treating the water that delivers nutrients to microorganisms within the filter.
- Sometimes the media within a bio-trickling filter can become blocked by the biomass growing within it and will need to be cleaned by a suitably qualified person.
- Water that passes through a bio-trickling filter becomes wastewater which usually needs treatment before it can be released into sewerage or drainage systems. In addition to this, wastewater from these filters can often contain sludge which needs to be stored and treated correctly. See the Liquid storage and handling guideline (EPA publication 1698) for more information on storing liquids. Information on proper methods to handle hazardous waste can be accessed through the WorkSafe document Safe handling of industrial waste: A practical guide for workplaces.
- Bio-trickling filters can be more effective at reducing odour than bio scrubbers as they do not require water re-circulation to work.
Even though these filters do not recirculate water, they are as water efficient as a bio scrubber or biofilter.
- Bioscrubbers need continuous monitoring of acidity (pH) and temperature within the filter. The pH can be kept within a broad spectrum, however, if the pH becomes too high or low (this will depend on your individual system), altering may be needed. The temperature should be kept between 15°C and 40°C with optimum temperature sitting between 30°C and 35°C.
- Simple adjustment of pH can occur as water is re-circulated through the system.
- Microorganisms are stored within a reservoir and circulated with water through the bioscrubber. Once passed through the bioscrubber, the solution is treated and re-circulated through the system, making bioscrubbers water efficient.
- Treating the solution before recirculation creates sludge, and wastewater. It is important that this sludge and wastewater is collected, stored, handled, and disposed of responsibly. See the Liquid storage and handling guideline (EPA publication 1698) for further information on storing liquids. Information on proper methods to handle hazardous waste can be accessed through the WorkSafe document Safe handling of industrial waste: A practical guide for workplaces.
This page was copied from EPA's old website. It was last updated on 4 June 2019.
Reviewed 1 October 2020