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A Chicken House Dust Buster.

Electrostatic system zaps airborne particles and pathogens

Negative air ion generators have been around for decades with user claims ranging from air quality improvement and sterilizing airborne bacteria to healing effects for burn patients and improving moods.

Most of the hundred or more commercial negative air ion generator products available today are said to improve air quality in enclosed spaces by charging dust particles in areas such as a room. The particles are collected and removed as air recirculates through the unit.

Although dozens of patents have been issued for such systems, technology adoption over the years has been limited because most of the devices have relatively low outputs and have not been tested for effectiveness.

Research in the early 1970s at the USDA Agricultural Research Service (ARS), Southeast Poultry Research Laboratory in Athens, Ga., focused on a different air cleaning system for poultry systems. Studies showed that filtering air with media-type filters rated at 95 percent efficiency nearly eliminated airborne virus transmission to chickens.

The concept proved useful for isolation cabinets but was impractical for open poultry areas where heavy dust levels can plug a high efficiency filter within about an hour.

The ARS research about 10 years ago changed to testing commercially available negative air ion generators to determine whether their dust reduction capability could reduce airborne transmission of poultry diseases. Early experiments showed that simple, commercially available ion generators reduced airborne transmission of Newcastle disease virus by about 30 percent.

These studies led to a Cooperative Research and Development Agreement (CRADA) with Simco Co., a large international electrostatics manufacturer in Hatfield, Penn., to develop an improved ionizer to generate higher ion densities in larger spaces to reduce airborne transmission of poultry diseases. Hatching cabinets were the first type of space studied because they are one of the primary sources for spreading salmonella in poultry.

The aim of the new electrostatic space charge system (ESCS) is to transfer a strong negative electrostatic charge to dust and microorganisms in an enclosed space. The charged particles are then collected on grounded trays, plates or room surfaces. Removing airborne dust in poultry areas reduces potential for airborne transmission of salmonella and other pathogens plus endotoxins and fungi such as aspergillus.

The ESCS showed an effectiveness comparable to the reduction offered by a 95 percent media filter for removing dust in laboratory experiments in hatching and transmission cabinets. Equal or better effectiveness occurred for removing airborne bacteria such as salmonella and Enterobacteriaceae.

Similar results surfaced for hatching cabinet experiments at the Richard Russell Research Center in Athens, Ga., in cooperation with researchers there, and for studies several months in commercial hatcheries. Experiments in a 15-foot X 22-foot (93.4-cubic-meter) isolation room with caged layers showed airborne salmonella enteritidis reductions of about 95 percent over a 10-day test period using the space charge system. Salmonella enteritidis is one of thousands of salmonella types. Only a few, including salmonella enteritidis, cause disease.

Besides reducing airborne dust and microorganisms, the space charge keeps surface dust near its source. For example, loose dust on the floor of a treated room stays there because once it leaves the floor it becomes charged, which reattracts it to the floor.

Basic lab experiments show that the charge also has a sterilizing effect that kills airborne and surface salmonella. The kill rate on airborne and surface salmonella at close range has been at least 98 percent.

Determining the charge density required for killing salmonella and other pathogenic bacteria is part of ongoing studies.

After about four years of research and development on the ESCS, which resulted in an effective system, a patent application was filed in 1998 and claims were accepted in February 2000. The new system uses a ground plane in close proximity to the discharge points.

An exclusive license for poultry applications has been granted to BioIon Inc. in Dallas, Ga., to distribute the system. The BioIon system has been tested in a commercial hatching cabinet and compared to a control cabinet that uses hydrogen peroxide disinfection. On average, in experiments ranging over five hatches, the BioIon system reduced salmonella fourfold over the control. It also reduced Enterobacteriaceae 94 percent over the control.

Poultry companies in the United States, Mexico, South America, Costa Rica, Japan, Korea, Israel and Holland have expressed interest in the system as a food safety intervention approach. A system for a typical commercial-sized, 15,000-egg hatching cabinet costs about $2,600 installed.

Advantages for a hatchery application include:

* improved food safety for consumers,

* reduced potential for cross contaminating other areas of the hatchery,

* reduced cleanup of exhaust ducts and open areas of the hatchery and

* improved air quality in hatchery exhaust.

Although technically effective for reducing the spread of salmonella in a larger room with cages, the economical feasibility for caged layer houses or other production houses is yet to be determined.

Another current study, with a large commercial poultry company, could determine if pathogen reductions using the ESCS at the hatchery reduce pathogens such as salmonella in birds arriving at a processing plant. It is possible that lower salmonella levels in or on birds leaving the hatchery will result in lower levels in production houses and at processing. These reductions could lead to improved food safety for consumers.

The U.S. president's Council of Food Safety has also identified the system as an intervention approach to be studied for reducing salmonella contamination in eggs -- another major food safety concern. Grant proposals are pending for research to:

* determine ESCS effectiveness in a broiler breeder house and

* determine the mechanisms and ion density level parameters required to kill 50 percent of bacteria (LD-50) for inactivating salmonella.

Other applications include using the system in any enclosed space where moderate to large concentrations of airborne dust or pathogens are generated or introduced. The system also reduces airborne particulates and pathogens in enclosed areas with normal concentrations of substances such as dust, pollen and bacteria. The applications have potential for improving human health.

ASAE member Bailey W Mitchell, a research agricultural engineer, recently received ARS recognition for his work on this project through a Superior Award for Technology Transfer.
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Title Annotation:negative air ion generators for air purification
Author:Mitchell, Bailey W.
Publication:Resource: Engineering & Technology for a Sustainable World
Date:Sep 1, 2000
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