2oOo Applied Pouluy Scimce, Inc REDUCING DUST IN A CAGED LAYER ROOM: AN ELECTROSTATIC SPACE CHARGE SYSTEM BAILEY W MITCHELL', PETER S. HOLT, and KUNHO SEO Southeast Poultry Research Laboratory, USDAIARS, 934 College Station Rd., Athens, GA 365 Phone: (76) 5463443 FM: (76) 5463161 Email: bmitcheli@seprl. us&.gov Primary Audience: Production Management, Quality Assurance Personnel, Researchers, Engmeers, Veterinarians DESCRIPTION OF PROBLEM Airborne dust in animal houses and its potential impact on human and animal health has been the subject of numerous reports for the last 2 yr. Sources of this dust include the animals, litter, feed, outside air, and secondary dust resuspended from building or equipment surfaces. Recent reports [l, 2,3,4,5,6] of dust levels and characterizations of dust components such as microorganisms, endotoxins, and odors measured in various types of animal housing have increased interest in dust reduc 1 To whom correspondence should be addressed tion options for these areas. Several approaches can reduce dust concentration in animal housing areas. These include adding fat to feed, fogging with water, fogging with an oilbased spray, regular washing, ionization, electrostatic filtration, vacuum cleaning, filtration and recirculation, cleaning with wet scrubbers, purge ventilation, deep litter, and optimization of air inlet position. Reductions reported with these approaches ranged from 15% for weekly washing of pigs and floors to 23% with ionizers to 76% with a rapeseed oil spray [2]. Use of canola oil at application rates on 29 April 218
Research Report MITCHELL et al. 293 averaging 1 ml/m2/day has been shown to reduce dust concentration in swine buildmgs by an average of up to 76% [A. Other reports of ionizer efficiency have ranged from 31% [8] to 67% [9] to 92% [lo]. In previous experimental studies, negative air ionizers have been shown to reduce airborne transmission of Newcastle Disease Virus [ll], to reduce airborne bacteria in a hatching cabinet [12], to reduce airborne transmission of Salmonella enteritidis in an isolation cabinet [13], to reduce airborne Salmonella in a caged layer room [14], and to reduce airborne Salmonella in a commercial hatching cabinet [lq. Most of the ionizer studies to date have utilized high voltage, negative air ion generators to develop an electrostatic space charge in an enclosed area. Chargingthe air means dust and other airborne particulate matter will also be charged, causing these substances to be rapidly attracted to grounded surfaces or to most walls, ceilings, and floors (grounded or oppositely charged) in proportion to the charge level. Charging the air will also cause particles to clump together and precipitate out faster. Other studies [16, 11 have shown that reducing airborne dust levels by 5% can reduce airborne bacteria by 1 fold or more. The purpose of the present study was to determine the effectiveness of a custom electrostatic space charge system with a high density output of negative air ions for reducing dust in a caged layer room as a means of reducing the airborne spread of pathogenic organisms. MATJWALSAND METHODS ROOM SETUP The experiments were conducted in temperaturecontrolled rooms with floor dimensions of approximately 15 ft x 22 ft and a 1 ft cehg (approximately 33 ft3 volume). The ventilation rate in each room was 211 ft3/min which provided 3.8 air changesb. A high density output ionizer [18] was suspended from the ceiling in the center of the treatment room (Room 1) such that its electrodes were 73 ft above the concrete floor as shown in Figure 1. The ionizer consisted of 222 electrodes on six bars operating at 3 kv, with a ground plane located above the bars. FIGURE 1. Layout of the caged layer room with ionizer EXPERIMENTAL DESIGN: SMOKE STICK TRIALS 'ho trials were conducted using a smoke stick (E. Vernon HiU, Inc., Benicia, CA) as a dust source. Previous experience with these smoke sticks and measurements of particle size distribution for the resulting smoke has shown that the smoke sticks generate a range of particle sizes primarily in the.3 to 5 micron range similar to the range generated by chickens. The procedure for the smoke stick trials was to place the smoke stick near the center of the treatment room (Room 1) at about 2 ft above the floor and initiate the smoke generation. Smoke was allowed to distribute throughout the room for 3 min, following which the smoke stick was removed for 3 min. The process was done first with the ionizer off, and following a 6min period for the air to clear, repeated with the ionizer on. Dust concentration was measured at the room exhaust at 1min intervals during the trials with a DustTrak laserbased instrument (TSI, Inc., St. Paul, MN). Particle size distribution was measured at the room exhaust at l5min intervals with a Climet CI5 laserbased instrument (Climet Instrument Co., Redlands, CA). Data stored internally on these instruments were dumped to a personal computer for analysis following the trials. Data for dust concentration and particle counts were compared using the Student's twotailed t test (Graphpad Software, San Diego, CA). on 29 April 218
294 ELECTROSTATIC DUST REDUCTION TRIALS WITH NATURALLY GENE RATED DUST FROM CAGED LAYERS One hundred twelve 56wkold White Leghorn hens were divided equally into two groups and placed into individual laying cages in the two rooms. Bird location was identical in each room. Room 1 was set up with the ionizer as described above, and Room 2 was used as the control room. Since only one particle size analyzer was available, measurements of particle size distribution were measured at 15min intervals from the front of the room exhaust by a 4 ft long, V4 I.D. sample tube for one 24hr period without the ionizer and two 24hr periods with the ionizer. For the dust concentration measurements, a DustTrak instrument was mounted outside of each room, and samples were pulled at 5min intervals from the front of the room exhaust by a 4 fi long, V4 I.D. sample tube. Dust concentration measurements were made continuously in both rooms for three 24hr periods. RESULTS AND DISCUSSION Use of the ionizer in the smoke stick trials slgruficantly (P <.OO1) reduced dust concentration (Figure 2). The amount of reduction varied from 72.3% (with the higher concentrations during the 3Omin interval the smoke stick was in the room) to 91% (during the 3min interval after the smoke stick was removed from the room). Particle counts were significantly (P<.OOOl) reduced at all size ranges and intervals during the smoke tests (Figures 3 and 4) except for the.3 to.5 micron range during the smoke stickin interval (Figure 3). The reduction amount in Amb*nt Sm*.SiickinPmSmdPWdror*Pm lncnml FIGURE 2. Average dust concentration reduction with and without ionizer using smoke stick as an artificial dust source 4. I, 1 35, 3, E 25. 3 2, 15, 1, 5,.3.5.51. 1.5. 5.1 1.25 Particle Size Range, Microns FlGURE3. Average particle count reduction with and without ionizer during the 3Omin period when smoke stick was in the room GolDnber m ionizer E W ~.3.5.51. 1.5. 5.1 1.25 Particle Sire Range, Microns flgure 4. Average particle count reduction with and without ionizer during the 3min period immediately after the smoke stick was removed from the room creased with increasing particle size range from a low of 3.9% to a h& of 86.3% for the smoke stickin interval. Reduction efficiency increased with the lower smoke concentrations during the smoke stickout interval (Figure 4) and ranged from a low of 72.2% to a high of 98.6%. The ionizer was also able to significantly (P <.OO1) reduce naturally generated dust from caged layers. Efficiencies for reducing dust concentration in the caged layer room ranged from 5 to 54% (Figure 9, considerably lower than the efficiencies obtained with the smoke stick. But the concentration levels generated by the birds were much lower (2 to 1fold) than those generated by the smoke stick. Experience with the system has shown that its efficiency is almost always lower at dust concentrations near ambient concentration (typically below.5 mg/m3). Particle counts in the treated caged layer room were significantly (P <.OOOl) reduced for all measurable particle size ranges up on 29 April 218
MITCHELL et al. Research Report 295 I Room 2 No Ion.5.45 5.4 'ii.35 7.3 E.25 3.2 6 E.15 g.1.5 3l27ll998 3/28/1998 3/29/1998 D.Y FIGURE 5. Average daily dust concentration reduction with and without ionizer with natural dust from caged layers FI NO Ionizer mlonizer Efficiency J 8, 1 7, 6, 'E 5. 'a, 4. U 5 3, n 2, 1,.34.5.51. 1.5. 5.1.1.25. Particle Size Range, Microns 9 8 5 7 2 6.: 5 5 4 6 3 3 2 2 1 a FIGURE 6. Average particle count reduction with and without ionizer with natural dust from caged layers to 25 microns (Figure 6). The >25 micron particle size range data were not included in the analysis of naturally generated dust since most counts were in this range. Reduction efficiency for the naturally generated dust ranged from 36.6% for the 3 to.5 micron particles to 65.6% for the 1 to 25 micron particles. Since no special collectors were provided for the charged dust particles, most of the dust collected on the walls and floor of the room, resulting in the exhaust filter in the ionizer room beii consistently cleaner and newer in appearance than the one in the control room. Although the dust reduction efficiencies achieved with the ionizer system in this study were not as high as have been reported for the same type of system in laboratory and commercialsized hatching cabinets [lo, 151, the system was sufficient to reduce airborne Salmonella enteritidis approximately 95% in later trials in the same rooms with the same chickens [14]. The ionizer unit selected for a 33ft3 room in the present trials was od half the size of the unit used in a 41 ft s commercial hatching cabinet, where dust concentration and air velocities were several times greater. CONCLUSIONS AND APPLICATIONS 1. A strong electrostatic space charge produced by a custombuilt ionizer can effectively and consistently reduce artificially produced dust from smoke sticks as well as dust naturally produced by chickens in a caged layer room. The 6bar, 222 electrode, 3 kv custom ionizer, which provided one discharge electrode per 14.9 ft3 of room volume, seemed adequate for the 33 ft3 room. 2. Dust concentration reduction is likely to be much htgher for dust levels well above the ambient level of concentration typically found in outside air. 3. The reduction efficiency, in terms of particle size distribution in the room application, increases rapidly with particle size and is typically higher than that indicated by dust concentration. A subsequent study with the same ionizer system and rooms in experiments with mature hens infected with Salmonella enteritidis showed that the ionizer reduced airborne Salmonella enteritidk by %.5% [14] and suggests that even moderate reductions in airborne dust can remove most of the airbornesazmonella. It would be reasonable to expect similar effectiveness in reducing other airborne bacteria, viruses, endotoxins, and mold spores that can be dispersed into the air or adhere to dust particles. A similar system could be used in any enclosed space where reduction of airborne dust and microorganisms is required, assuming it is acceptable for the walls and floors to collect the extra dust from the process. It would be possible to reduce collection on the walls by using specialized collector trays or plates as in earlier studies in hatching cabinets [12, 151. Although the ionization units described herein will distribute a strong charge for several on 29 April 218
2% JAPR ELECTROSTATIC DUST REDUCTION feet in an enclosed space without any air movement, it is best to locate an ionizer unit or units such that air coming into the space or recirculating in the space will pass by it thus helping to distribute the charge in the space. For example, in a house setting it might be desirable to place a unit in front of the air inlet or in front of a stirring fan. Ion distribution does not lend itself to ducts because they will drain the charge from the air. 6. Although technically feasible for commercial poultry production houses, this ion system needs further studies to determine the economic feasibility for larger areas. It would probably be easier initially to justify the expense of the system for primary breeder flocks than for common layer or broiler houses. 1. Takai, H.,J. Seedort, and S. Pedersen, 1999. Dust and endotoxin concentrations in liitock buildings in Northern Europe. P ap 8389 in: Proc. Intern. Symp. on Dust Control in Animal Production Facilities, Danish Institute of Agric. Sci., Bygholm, Denmark. 2. CIGR Working Group 13,1994. Climatization and environmental control in animal housing. Pa es 83112 in: Aerial Environment in Animal Housing: hncentrations in and Emissions from Farm Buildings. CIGR and CEMAGREP, Report No. WG No 94.1, Rennes Cedex, France. 3. Him, T., J. Hnrtung, and B. Wiegand, 1994. Air quality in a Louisianatype boiler house. Report No. 94(28, AgEhg Milano 94, Milano, Italy. 4. Martensson, L, 1995. Concentrations of Dust, Endotoxin, and Organic Acids in Confined Animal Buildings. Thesis, Dept. of Agric. Bi tems and Tech., Swedish Univ. of Agr. Sci., Lund, Swxn. 5. Pearson, CC. and TJ. Sharpies, 1995. Airborne dust concentrations in liitock buildings and the effect of feed. J. Agr. Engineering Res. 6(3):14554. 6. Simpson, J., R.M. Niven, C. Pickering, LA. Oldham, A.M. Fletcher, and H.C. Francis, 1999. Comparative personal exposures to organic dusts and endotoxin. Annals of Occupational Hygiene 43(2):17115. 7. Zhnng, Y., A. Tannks, EM. Barber, and JJ.R Peddes, 1996. Effects of frequency and quantity of?rinkling canola oil on dust reduction in swine buildings. ram. of AS 39(3):177181. 8. Czarick, M.I., G.L Van Wicklen, and Rk Clemmer, 1985. Negative air ionization for swine during weaning. Pa er 85451, ASAE Annual Meeting, St. Joseph, Mf: 9. Veeohnipn, MA. and D.S. Bun@, 199. Electrostatic precipitation dust removal system for swine housing. Paper 9466., ASAE Annual Meeting, St. Joeph, MI. REFERENCES AND NOTES 1. Mitchell, B.W., 1998. Effect of negative air ionization on ambient particulates in a hatching cabinet. Appl. Engineering in Agr. 14(5):551555. 11. Mitchell, B.W. and DJ. King, 1993. Effect of negative air ionization on airborne transmission of Newcastle Disease Virus. Avian Dis. 385 25732. 12. Mitchell, B.W., RJ. Buhr, M.E Berrang, J.S. Bailey, m d NA Cox, 1998. Reduction of airborne bacteria in the hatching cabinet with an electrostatic space charger. Poultry Sci. 77(S1):151. 13. Cast, RE, B.W. Mitchell, and P.S. Holt, 1999. Application of negative air ionization for reducing experimental airborne transmission of SalmDnella enteritidis to chicks. Poultry Sci. 78(1):5741. 14. Holt, P.S., B.W. Mitchell, K.H. Seo, and RK. Gas4 1999. Use of negative air ionization for redufing airborne Ievelsof~~serovarEntentldls in a room containin infected caged layers. J. Appl. Poultry Res. 8 : d 15. Mitchell, B.W., 1999. Electrostatic space charge system for dust and pathogen removal in commercial hatching cabinets. Poultry Sci. 78(S195):143. 16. Madelln, T.M.and C.M. Wathes, 1988. Air hygiene in a broiler house: Comparison of dee litter with raised netting floors. Br. Poultry Sci. 3:2%3!. 17. Carpenter, G.A., W.K. Smith, A.P.C. MacLaren, and D. Spackman, 1986. Effect of internal air filtration on the rformance of broilers and the aerial concentrations opedust and bacteria. Br. Poultry Sci. 274714. 18. Mitchell, B.W.and H.S. Stone, 1998. Electrostatic reduction system for reducing airborne dust and microorganisms. Patent Application Serial No. 9/122,85. Filed July28,1998. Claims accepted February, 2OOO. on 29 April 218