Grantee Research Project Results
Final Report: Electrostatically Charged Aerosol Decontamination System for Small Building Decontamination
EPA Contract Number: 68D02083Title: Electrostatically Charged Aerosol Decontamination System for Small Building Decontamination
Investigators: Athanassiu, Christos
Small Business: Foster-Miller Inc.
EPA Contact: Richards, April
Phase: I
Project Period: September 30, 2002 through March 31, 2003
Project Amount: $69,992
RFA: Small Business Innovation Research (SBIR) - Phase I (2002) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , SBIR - Air Pollution , Small Business Innovation Research (SBIR)
Description:
The purpose of this research project was to develop a method for effectively decontaminating the interior of a typical small office building as well as the building's heating, ventilation, and air conditioning (HVAC) system. The method of decontamination developed by Foster-Miller is efficient and effective, and minimizes the collateral damage to the building.
Foster-Miller developed a method of delivering any aqueous decontamination solution in an efficient and effective means with minimal waste and collateral damage to the material and surroundings. This decontamination method is called Electrostatically Charged Aerosol Decontamination (ECAD). The technology works by first taking any aqueous decontaminate and breaking it up into small droplets using high-pressure compressed air. These reagent droplets then are charged using a high-voltage charging system as they exit an atomizing nozzle. The resulting charged droplets are light enough and small enough to be easily distributed across large and complex surface areas. These charged droplets are propelled throughout the contaminated area because positively charged droplets repel each other at very high velocities and then are driven by their highly positive charge to all services of lower electrical potential. As a result of the high-velocity distribution of these reagent droplets, they provide the potential for collisions with any chemical/biological (C/B) agent droplets that remain airborne after a C/B release. In addition, because of the very high positive charge on the reagent droplets:
- All surfaces within the range of the ECAD System are coated with the charged decontamination solution.
- The amount of decontamination solution and the duration of contact with the potentially contaminated area and surface can be controlled by the rate of delivery and the level of electrical charge.
- The system can be set up and allowed to operate without direct operator involvement in the potentially contaminated area.
- The amount of reagent required for decontamination of a given area is reduced significantly because only the surfaces are covered.
- In most cases, clean up of residual decontamination products after the process is not required due to the minimum amounts applied, further reducing the potential for consequential damage to materials and property.
Summary/Accomplishments (Outputs/Outcomes):
Building Interior Decontamination
Several different ECAD System configurations were tested in a simulated office test facility constructed at Foster-Miller's offices in Waltham, MA. Initially, each test configuration was run through a series of wetting effectiveness tests. These tests were designed to optimize the ECAD System's distribution effectiveness in spraying water into the simulated office test facility. Using a moisture-collection system distributed throughout the room, the distribution effectiveness of the water spray was evaluated and optimized. The most effective system configuration was determined using this process and was selected for additional testing with live anthrax simulant and other live Class II microorganisms. The final ECAD test configuration is shown in Figure 1.
Figure 1. ECAD system configuration.
The ECAD System was used to conduct live anthrax simulant using Bacillus globigii as the simulant in the simulated office test facility. Simulant spores ware placed on petri dishes and allowed to germinate and develop colonies. These colonies were counted on one representative sample to establish a base condition. Several sets of dishes were prepared and delivered to the simulated office test facility for several series of decontamination exercises to evaluate the effectiveness of the ECAD System. The decontamination solution selected for this demonstration is a newly developed, nontoxic, non-corrosive commercial disinfectant made by EnviroSystems, Inc., called EcoTru®. The EcoTru® disinfectant has been approved by the U.S. Environmental Protection Agency (EPA) for use on a variety of Class II microorganisms and fungi. The initial testing was performed to determine if the ECAD System would in any way impact the effectiveness of EcoTru®. To address this, a control test was performed in which EcoTru® was sprayed onto the populated dishes using a standard pump spray bottle, the standard method of delivering EcoTru®. A second set of dishes was sprayed using the single-nozzle ECAD System with the electrical charging ring disabled. This test was designed to determine whether the method of liquid atomization would impact efficacy. A third set of dishes with simulant then were sprayed with the single-nozzle ECAD System and with the charging ring energized. All of the samples then were returned to the laboratory for incubation and assessment. The results showed a minimum of a 4-log kill on all samples except for untreated control samples, which multiplied as expected.
A second series of tests were performed to establish the distribution effectiveness of ECAD in delivering EcoTru® with the same type of simulant on the dishes. In this test, simulant dishes were distributed around the room in various locations. The automated ECAD System then was used to deliver the EcoTru®. Two different durations on separate dishes were run, one 10 minutes in duration, and another 20 minutes in duration. After each test, the sample dishes were returned to the laboratory for incubation. The test results showed that samples sprayed with all three methods showed a minimum of a 3-log kill on all dish samples.
Similar tests were performed using the same process on three different Class II microorganisms, Staphylococcus aureus, Pseudomonos aeruginosa, and Streptococcus under the supervision of Dr. Howard Sussman, Director of Infection Control at Stanford University Hospital, Palo Alto, CA. Results of this controlled test using ECAD delivering EcoTru® showed the same basic results, demonstrating that the ECAD System is an effective and efficient means of decontaminating surfaces in large, open areas.
HVAC Duct Decontamination
In addition to demonstrating building interior decontamination, ECAD technology was used to demonstrate how an HVAC duct system might be decontaminated using the same charged-spray technology. A series of tests were conducted spraying charged water droplets into a section of HVAC duct set up in the laboratory shown in Figure 2. The duct testing showed some interesting results. Initially, the duct was ungrounded as the charged water droplets were sprayed into one end of a 10' x 5' "L" shaped section of duct. In this configuration, water droplets could be seen exiting the duct at the other end of the L configuration. Later, this same duct setup was modified by grounding the duct and there was a dramatic change in the results. Even though the same amount of charged droplets was being sprayed to the inlet end of the duct section, no water droplets were seen exiting the duct. This is a direct result of the charged droplets being attracted to the metal duct surface. When the duct was ungrounded, some of the droplets were able to make their way through the entire duct without being pulled to the metal surface. These results demonstrate that the amount of duct wetting and wetting distribution can be directly controlled by adjusting the ground potential of the duct. This behavior will enable decontamination of a range of sizes and lengths of HVAC ducts in buildings using ECAD that assures complete and uniform wetting based on setting up the proper ground potential of various sections of duct. For instance, in a long section of duct the potential along the duct can increase gradually so as to assure that the decontamination solution is evenly distributed along the entire length of duct.
Figure 2. HVAC duct decontamination demonstration.
Conclusions:
ECAD technology can be used to effectively and efficiently deliver any aqueous decontamination solution, reagent, or disinfectant for a wide range of industries and applications. Several applications currently are being developed by Foster-Miller and its partners to include the following:
- Mass Transit Facility Decontamination. Foster-Miller has been in discussions with the Federal Transit Administration and the Transportation Security Administration for the use of ECAD for decontamination of subway systems that may become contaminated due to a C/B attack. The concept is for two systems to be used by subway authorities, one for first response to minimize the spread and conduct initial clean up, and a second system for post-event restoration. Figure 3 shows a concept for the first response system. Figure 4 is an illustration of the facility restoration system.
Figure 3. First-response system for deployment in subway station.
Figure 4. C/B attack ECAD subway restoration system.
- Cruise Line Shipboard Disinfecting. Foster-Miller and EnviroSystems, Inc., held discussions with several cruise lines recently at the Sea Trade Show in Miami. EnviroSystems has developed an EPA-approved disinfectant that recently has been demonstrated to be effective against the Norwalk virus. Foster-Miller and EnviroSystems currently are planning a demonstration with one of the major cruise lines to present the ECAD delivery system and its ability to efficiently deliver disinfectant on large commercial ships.
- Chemical Demilitarization Decontamination. Foster-Miller has been applying and continues to market ECAD technology to the U.S. Army's Chemical Demilitarization programs for applications in equipment, facility, and personnel decontamination, as well as for other military applications including ground equipment, aircraft, military installations, and personnel decontamination.
- Hospital Infection Control. Foster-Miller and its partner EnviroSystems have conducted demonstrations and are in ongoing discussions with Stanford University Hospital in Palo Alto, CA, and Massachusetts General Hospital in Boston, MA, for use of ECAD technology in hospital infection control. The concept is to use ECAD to control infection outbreaks by disinfecting areas that have high exposure or that have been identified as "high-risk-of-spread" areas.
- Animal Breeding Facility Outbreak Control. Foster-Miller has met with principals of Charles River Laboratories, the largest animal breeding facility in the world, to discuss applications of ECAD for breeding facility outbreak control.
Supplemental Keywords:
Electrostatically Charged Aerosol Decontamination System, ECAD, charged spray, chemical/biological agent, bioterrorism, Class II microorganisms, anthrax, Staphylococcus aureus, Pseudomonos aeruginosa, Streptococcus, EcoTru, liquid atomization, HVAC, duct, mass transit facility, subway, cruise line, chemical demilitarization, hospital infection control, animal breeding facility, SBIR., Scientific Discipline, Air, Environmental Chemistry, Analytical Chemistry, Biochemistry, Atmospheric Sciences, Engineering, Chemistry, & Physics, homeland security, decontamination, chemical treatment, biological warfare agents, pathogenic microbes, bioterrorism, smallpox, anthrax, microbial contaminantsThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.