Fan Assisted Filters: How They Work
Fan assisted filters fall into the broad category of carbon filters. They are very effective to remove organic compounds from the air, which eliminates the odours caused by those compounds.
- Fan assisted filters remove up to 99.5% of odorous gases from the source.
- Carbon filters are made by treating charcoal with oxygen.
- They can be used on municipal sewer systems to reduce odours, and improve relations with neighbours.
Read on to find out exactly how they work below, or get product-specific information about fan assisted filters here.
What is activated carbon and how does it work?
Carbon filters are made by treating charcoal with oxygen, so that the oxygen atoms open up millions of pores between the carbon atoms. The result is a huge surface area of carbon atoms within a very small block of charcoal. Activated Carbon is the term given to charcoal that has been treated with oxygen.
When other organic gases pass through the activated carbon bed, the carbon attracts the gas molecules, which stick to the open surface that has been created. This chemical attraction is called adsorption.
Once the molecules stick to the carbon site, they are trapped there - using up that site. Once all the sites are used, the carbon filter is spent and must be replaced.
What is a fan assisted filter?
Fan assisted filters do not rely on the natural flow of air to capture gases through the carbon filter. Instead, a fan draws the gases from the source and into the filter. This is to prevent the escape of gases from other vents or leaking seals and into the atmosphere.
For high volumes where odours are otherwise likely to escape, fan assisted filters are the ideal solution to avoid odour complaints.
One configuration places the fan upstream of the filter - thus sucking gas from the source and then pushing it through the filter. Another configuration is to place the fan downstream of the filter - as such, sucking the gas from the source, through the filter and then pushing it out into the atmosphere.
OdourPro uses pellets made of high performance activated carbon, which target H2S adsorption. The filter media also reduces dimethyl sulphide, mercaptans and Volatile Organic Compounds (VOCs). Fan assisted filters remove up to 99.5% of odorous gases from the source.
Fan assisted filters are preassembled for easy installation on site. They consist of a High-Density Polyethylene (HDPE) vessel, a fan and a PLC control panel. The fan requires three phase power to operate. Manual switch operations and indicator lights clearly show the operational status. For critical applications, a backup fan is automatically switched on in an emergency.
It is very important to install a non-return inlet air valve on the wet well. This valve draws fresh air into the system to replace the noxious gas removed through the filter.
Where are fan assisted filters used?
Fan assisted filters are often used on municipal sewer systems to reduce odours and improve relations with neighbours.
Sewer systems are vulnerable to the release of odours during peak usage in the mornings and evenings. Large flow rates and constant activation of pump stations to keep the waste flow moving towards treatment plants generate more gases and higher pressures in the pumps stations, rising mains and air valves. These higher gas pressures result in emissions through vents and leaking seals at higher rates than normal. The “fugitive” emissions often lead to odour complaints.
Fan assisted filters create a slightly negative pressure in the sewer system by drawing the gas out, therefore eliminating the possibility of gas emissions and odour complaints.
Get a customised design
OdourPro has a specialised design and installation process created to produce an efficient system that suits the specific site needs. Information is collated about the wet well or chamber to be treated. Measurements of wastewater inflow rates and air space volume enable capacity calculations of the filter. Analysis of the composition of odorous compounds ensure correct selection of filter media.
Units get prefabricated at the OdourPro workshop and shipped to site as a turnkey solution. Pre and post filter air testing evaluates the performance of the fan assisted filter compared to design criteria.
Contact OdourPro for more information about fan assisted filters
OdourPro has extensive experience in fan assisted filter systems. We have access to a range of filter technologies so that we can apply the most effective solution to your site.
OdourPro on 21 November 2016
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