Biofilters for air pollution control

Social IssuesEnvironment

  • Author Don Milne
  • Published January 13, 2018
  • Word count 516

Biofiltration has always been an existing concept for air pollution control deriving from as early as 1923 where biological methods were proposed to treat odorous emissions.

Advancements in research and technology started in Germany circa 1955 with biofilter treatments applied to address odorous emissions in low concentrations with a high success rate witnessed in Germany in the 1970s.

This success led to further research being developed in the United States and other parts of Europe in the 1980s with external outreach to the rest of the world. By the 1990s, there were more than 500 recorded biofilters in operation both in Germany and Netherlands with a widespread trend starting in the United States.

What is Biofiltration?

Biofiltration is essentially an air pollution control technique involving biodegradation of contaminants. These contaminants are biodegraded by microorganisms that are diffused in a thin layer of moisture referred to as biofilm.

The main use is for the elimination of malodorous gas emissions and low concentrations of volatile organic compounds.

What makes a Biofilter and How does it Work?

The components of a biofilter include a biofilter bed, a support rack, and a fan.

The materials used for the biofilter bed often include peat, compost, soil, gravel, or plastic bits.The support rack is designed to be perforated to allow air flow between the plenum and the biofilter bed allowing contact of the microbes inside the bed material. The purpose of the fan is to collect contaminated air allowing emissions to flow through and for the pollutants to be absorbed in the moisture of the biofilter bed.

The microbes found within the bed material consume and metabolise the pollutants thus reducing the concentrations of the pollutants.

Different Types of Biofilters

There are three main variations of biofilters pertaining to the layout, shape, and bedding media.

On the basis of the biofilter layout, there is a variation for either an open bed which is uncovered and exposed to all weather conditions and a closed bed which contains a small exhaust vent.

On the basis of shape, the biofilter could be designed horizontally (which leaves a larger carbon footprint, is relatively inexpensive, and is easy to maintain) or could be designed vertically (which reduces the carbon footprint, uses a lesser surface area, requires more maintenance, and is higher in cost to build).

With regards to the bedding media, there are two variations which are organic compost or synthetic media. Organic compost typically has an effective lifespan of around 5 years while synthetic media has a longer effective lifespan.

Benefits of Biofiltration

The use of biofilters to treat air pollution leaves a positive environmental footprint through the absence of chemicals and toxins. Not only does it benefit the ecosystem, the effectiveness of biofilters is evident in its ability to remove air pollutants at a low operating cost.

Biofilters follow the laws of conservation and mass balance which acts in accordance with mother nature. In setting up a biofilter system, it is critical that developers acquire a detailed understanding of the environmental site, conditions, limitations, components, logistics, and safety measures in order to set up an efficient biofilter system.

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