Biofilter: Expanded Definition
COMM213 Technical Communications @Humber College \ Toronto 2009
INTRODUCTION
A biofilter is a vertically mounted, indoor air cleansing system of rooted, living plants that naturally break down and remove harmful contaminants from the atmosphere. Sealed off from outside weather elements, interior air spaces in Canada's well-insulated buildings are increasingly scrutinized for safety. Air quality in confined spaces deteriorates over time; chemicals leach from common sources–--such as cleaning agents and paint—--jeopardizing the health of occupants as dangerous particles build up in closed systems. Standard air improvement measures involve bringing in fresh outside air, but complicated filtration and heat exchange requirements of mechanized intake systems often prove expensive to install, operate and maintain. First trialled in the 1990s, biofiltration is a relatively simple, reliable and inexpensive alternative. Adapted from nature, it requires little maintenance and no infrastructure modification. A biofilter improves air quality not only by reducing air-borne chemicals, but also by producing oxygen and temperature stabilizing humidity. Research and technology is currently expanding to explore further performance and application possibilities.
PARTS ANALYSIS
The foundation of a biofilter is two one-inch permeable sheets of plastic mesh affixed to a waterproofed wall. The support surface must be sturdy, such as a heavy metal frame or concrete wall, able to bear the weight of several gallons of water in addition to the filtration system itself. Numerous plants are stacked vertically between the mesh layers, protruding horizontally through slits on the surface material sheet. Their root systems aggregate as a vertical organic layer between the mesh. A pump at the base of the wall continuously cycles water back to the top in order to feed and water the plants, circulate pollutants to the plant roots for treatment, and prevent standing water mould growth. The biofilter system must be drained once a month to ensure proper working conditions of the parts, and healthy roots must be encouraged through periodical plant maintenance of dusting and pruning.
OPERATING PRINCIPLES
The biofilter's main function is to improve indoor air quality by removing air contaminants. Particle pollutants in passing air currents deposit into the trickling wall water, continuously circulating through the mesh wall's gravitational drip system facilitated by a pump. As contaminated water makes contact with the plant roots, naturally occurring host microbes on root surfaces quickly break down the toxins: in just one cycle nearly all formaldehyde may be eliminated, for example. A biofiltration system can be used to clean ambient surrounding air or it can play a larger role in building-wide ventilation mechanisms.
EXAMPLES
There are several existing biofilter projects in Canada, including the largest in the world at the University of Guelph-Humber building at the Humber College campus in Toronto. The wall is 30' x 55' within a four-storey main entrance hall, sited for daylight and aesthetic. Incorporated at the design-concept stage, the biofilter is integrally connected to the building's ventilation system and supplies full capacity of clean replacement air for that which is externally exhausted. A collaboration project between the University of Guelph and the Humber Institute of Technology and Advanced Learning, this biofilter is employed not only as an air quality device but as a teaching tool and research study for development of the future of biofiltration.
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COMM213 Technical Communications @Humber College \ Toronto 2009
INTRODUCTION
A biofilter is a vertically mounted, indoor air cleansing system of rooted, living plants that naturally break down and remove harmful contaminants from the atmosphere. Sealed off from outside weather elements, interior air spaces in Canada's well-insulated buildings are increasingly scrutinized for safety. Air quality in confined spaces deteriorates over time; chemicals leach from common sources–--such as cleaning agents and paint—--jeopardizing the health of occupants as dangerous particles build up in closed systems. Standard air improvement measures involve bringing in fresh outside air, but complicated filtration and heat exchange requirements of mechanized intake systems often prove expensive to install, operate and maintain. First trialled in the 1990s, biofiltration is a relatively simple, reliable and inexpensive alternative. Adapted from nature, it requires little maintenance and no infrastructure modification. A biofilter improves air quality not only by reducing air-borne chemicals, but also by producing oxygen and temperature stabilizing humidity. Research and technology is currently expanding to explore further performance and application possibilities.
PARTS ANALYSIS
The foundation of a biofilter is two one-inch permeable sheets of plastic mesh affixed to a waterproofed wall. The support surface must be sturdy, such as a heavy metal frame or concrete wall, able to bear the weight of several gallons of water in addition to the filtration system itself. Numerous plants are stacked vertically between the mesh layers, protruding horizontally through slits on the surface material sheet. Their root systems aggregate as a vertical organic layer between the mesh. A pump at the base of the wall continuously cycles water back to the top in order to feed and water the plants, circulate pollutants to the plant roots for treatment, and prevent standing water mould growth. The biofilter system must be drained once a month to ensure proper working conditions of the parts, and healthy roots must be encouraged through periodical plant maintenance of dusting and pruning.
OPERATING PRINCIPLES
The biofilter's main function is to improve indoor air quality by removing air contaminants. Particle pollutants in passing air currents deposit into the trickling wall water, continuously circulating through the mesh wall's gravitational drip system facilitated by a pump. As contaminated water makes contact with the plant roots, naturally occurring host microbes on root surfaces quickly break down the toxins: in just one cycle nearly all formaldehyde may be eliminated, for example. A biofiltration system can be used to clean ambient surrounding air or it can play a larger role in building-wide ventilation mechanisms.
EXAMPLES
There are several existing biofilter projects in Canada, including the largest in the world at the University of Guelph-Humber building at the Humber College campus in Toronto. The wall is 30' x 55' within a four-storey main entrance hall, sited for daylight and aesthetic. Incorporated at the design-concept stage, the biofilter is integrally connected to the building's ventilation system and supplies full capacity of clean replacement air for that which is externally exhausted. A collaboration project between the University of Guelph and the Humber Institute of Technology and Advanced Learning, this biofilter is employed not only as an air quality device but as a teaching tool and research study for development of the future of biofiltration.
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