#05-132

Complete

Date Full Report Received

07/16/2007

Date Abstract Report Received

07/16/2007

The objective of this study was to test the effectiveness of a commercially available biocurtain, incorporating an electrostatic space charge system (ESCS), at reducing dust emissions from a commercial wean-to-finish swine building. The study was carried out using a tunnel-ventilated, 1,100-head building with curtain sides and a deep pit. Two biocurtains were installed on the building. One covered the six room-exhaust fans (five 122-cm diameter and one 91-cm diameter) and the other covered one of the four 46-cm diameter pit-exhaust fans. The room-exhaust fans came into operation when the room temperature exceeded the thermostat set point with the 91-cm diameter variable-speed fan being the first into operation followed by the five 122-cm diameter fixed-speed fans which came into operation in sequence. The four pit-exhaust fans were fixed speed and were in continuous operation.

The effectiveness of the biocurtains, covering the room-exhaust and pit-exhaust fans, either with or without the ESCS system in operation, was evaluated by estimating dust emissions at three points, namely in the exhaust air before the room-exhaust or pit-exhaust fans and in the exhaust air at the top exit of and coming through the biocurtain. Dust emissions were estimated from measurements of dust concentrations, using a Total Suspended Particle Isokinetic Sampler developed at the University of Illinois, and measurements of ventilation rates at the three points of measurement. Airborne bacteria concentrations were measured at the same three measurement points as used for the dust emissions measurements. Two trials were carried out, with Trial I being undertaken between the months of July and October 2006, and Trial II being carried out in two replicates in August 2007 and November/December 2007, respectively. Thus, the evaluation of the effectiveness of the biocurtain was carried out under conditions representing a range of levels of dust emissions from relatively low in November and December to maximum levels in the warmer summer months. During Trial I and Replicate 2 of Trial II, the biocurtain was operated for one week with the ESCS switched on followed by one week with it switched off. Consequently, it was not possible to directly compare the efficiency of the biocurtain for dust removal with and without the ESCS because this comparison was confounded with week of study.
Dust retention rates for the biocurtains (i.e., the difference between the amount of dust in the air flowing through room-exhaust or pit-exhaust fans and that measured at the top exit of or going through the biocurtain) for Trials I and II averaged 62% with a range from ~30 to 90%. The lowest retention rates for both biocurtains (28% and 32% for the biocurtains covering the room- and pit-exhaust fan, respectively) were observed in Replicate 1 of Trial II which was carried out in August. Retention rates were, on average, higher with the ESCS system on than off (78% vs. 69%, respectively) and for the biocurtain covering the pit-exhaust fan than for that covering the room-exhaust fans (68% vs. 56%, respectively). Concentrations of airborne bacteria were lower at the top exit and immediately outside of the biocurtain compared to concentrations in the exhaust air flowing through the room- and pit-exhaust fans.
The results of this study suggest that the biocurtain technology evaluated was effective at reducing dust emissions and bacterial concentrations in the exhaust air stream from conventional commercial swine facilities. Further research is required to understand the causes of variation in the effectiveness of the biocurtain observed in this study.