Capturing airborne particles from air into a liquid is a critical process for the development of many sensors and analytical systems. A miniaturized airborne particle sampling device (microimpinger) has been developed in this research. The microimpinger relies on a controlled bubble generation process produced by driving air through microchannel arrays. The particles confined in the microscale bubbles are captured in the sampling liquid while the bubbles form, are released and travel in a millimetre-scale sealed liquid reservoir. The microchannel arrays in the impinger are fabricated using a soft-lithography method with polydimethylsiloxane (PDMS) as the structural material. To prevent air leakage at the connections, a PDMS-only sealing technique is successfully developed. The hydrophobicity of the microchannel surface is found to be critical for generating continuous and stable bubbles in the bubbling process. A Teflon layer is coated on the walls of a microchannel array by vapor deposition which effectively increases the hydrophobicity of the PDMS. The collection efficiency of the microimpinger is measured by counting different sizes of fluorescent polystyrene latex particles on polycarbonate membrane filters. Collection efficiencies above 90% are achieved. Furthermore, the particle capturing mechanisms during the injection, formation and rise of a single microbubble are investigated by a computational fluid dynamics (CFD) model. The Navier–Stokes equations are solved along with the use of the volume-of-fluid (VOF) method to capture the bubble deformations and the particles are tracked using a Lagrangian equation of motion. The model is also employed to study the effect of bubble size on the collection efficiency of the microimpinger.

A microfluidics-based on-chip impinger for airborne particle collection.

A number of chain restaurants, retailers, and grocers in the U.S. have pledged to source only cage-free (CF) eggs in the foreseeable future (e.g., by 2025) due to marketing reasons or concerns over animal welfare. However, CF housing has some inherent challenges, and a predominant one is poor air quality, i.e., ammonia gas (NH3) and particulate matter (PM), and increased emissions. Spraying a liquid agent such as electrolyzed water (EW) can effectively suppress PM generation of CF henhouse litter. However, liquid spray can enhance NH3 generation because it increases the litter moisture content (LMC). Application of acidic liquid to the litter would help control NH3 while suppressing PM, but concerns arise about the potential corrosive effect of acidic liquid on housing equipment. To overcome this dilemma, this study evaluated the effect of applying PLT, a commercial poultry litter additive (LA), on NH3 emissions of CF hen litter while spraying it with neutral EW (NEW) at a rate of 25 mL kg-1 dry litter d-1. The PLT application rates were 0.3, 0.6, and 0.9 kg m-2, denoted as Low-LA, Med-LA, and High-LA, respectively. CF litter was placed inside dynamic emission chambers and automatically stirred to mimic hen scratching. PLT was topically applied onto the litter on day 1; NEW was sprayed daily for 11 d, followed by a 3 d non-spray period (i.e., 14 d per trial); and each regimen was replicated four times. The ammonia emission rate (ER) of the control (no LA), Low-LA, Med-LA, and High-LA regimens (mean ±SE) was, respectively, 0.76 ±0.05, 0.55 ±0.06, 0.37 ±0.04, and 0.16 ±0.02 g kg-1 dry litter d-1, i.e., 28% to 79% reduction by the treatments. The NH3 reduction efficiency was linearly proportional to the PLT application rate, with higher application rate resulting in lower litter pH (p

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=2215&context=abe_eng_pubs

Mitigating ammonia and PM generation of cage-free henhouse litter with solid additive and liquid spray.

. Particulate matter (PM) concentrations are high in cage-free aviary hen houses due to accumulation of litter on the floor and hen activities. The use of a spraying agent such as acidic electrolyzed water (AEW) to mitigate PM levels and disinfect houses has been reported, and high spray dosages will reduce PM to a low level. However, spraying a high dose of AEW may generate high levels of ammonia (NH3) due to an increase in litter moisture content (LMC). Lab-scale experiments were conducted to assess the effect of AEW spray dosage and pH on PM and NH3 emissions from the litter of aviary hen houses. Four dynamic emission chambers (DECs) located in an environmentally controlled room were used for the evaluation. Three spray dosages of 25, 50, and 75 mL kg-1 dry litter d-1 (equivalent to area application rates of 125, 250, and 375 mL m-2, respectively) and three pH values of 3, 5, and 7 at a free-chlorine concentration of 200 mg L-1 were tested. Spraying occurred within 10 min once a day for five consecutive days. A no-spray regimen was used as the control. The results showed that higher spray dosages of AEW led to lower PM emissions. In particular, spraying dosages of 25, 50, and 75 mL kg-1 dry litter d-1 reduced PM levels by (mean ±SD) 71% ±3%, 81% ±1%, and 89% ±1%, respectively, immediately after spraying. The PM reductions were still significant 24 h after spraying, averaging 57% ±4%, 71% ±5%, and 83% ±1%, respectively. There was no significant difference (p = 0.30 to 0.43) in reduction efficiency among the PM sizes (i.e., PM1, PM2.5, PM4, PM10, and total suspended particulates). For NH3 emissions, spraying 75 mL kg-1 dry litter d-1 generated 5 to 6 times greater NH3 emissions when compared to 25 mL kg-1 dry litter d-1 due to the difference in LMC (22.6% vs. 13.0%). Meanwhile, spraying AEW of pH 7 yielded 2 to 3 times higher NH3 emissions than AEW of pH 3 at the same dosage. Ammonia emissions of all spray treatments were found to be higher than that of the control, albeit no significant difference between the control and the 25 mL kg-1 dry litter d-1 dosage at pH 3 or pH 5 (p = 0.81 and 0.47, respectively). Pearson correlation coefficients between NH3 and spray dosage (0.82) and pH value (0.46) indicated that spray dosage is more linearly correlated to NH3 emissions than pH value (p

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=2086&context=abe_eng_pubs

Reduction of Particulate Matter and Ammonia by Spraying Acidic Electrolyzed Water onto Litter of Aviary Hen Houses: A Lab-Scale Study

Mitigating airborne bacteria generations from cage-free layer litter by spraying acidic electrolysed water

Abstract. Compared to conventional cage production systems, cage-free (CF) hen housing offers hens more space and opportunities to exercise their natural behaviors (e.g., perching, dust bathing, and foraging). However, CF housing poses a number of inherent environmental challenges, among which are high levels of particulate matter (PM) and ammonia (NH3). Spraying water on CF hen house litter (e.g., 125 mL m-2 per cm of litter depth) has been shown to mitigate generation of PM by 60% to 70% in our previous lab-scale tests. The objectives of this study were to verify the lab-scale findings of PM reduction in a commercial CF hen house in central Iowa and to evaluate the indoor air quality (e.g., PM and NH3 concentrations) and litter moisture content as affected by water spray. The commercial CF house had a nominal capacity of 50,000 laying hens and measured 154 m × 21.3 m × 3.0 m (L × W × H). A water sprinkling system was installed in half of the hen house in the length direction (treatment section), while the other half of the hen house served as the control. For each of the three trials conducted during the winter of 2017-2018, spray dosage (125 mL H2O m-2 per cm of litter depth) was set according to the initial litter depth before spraying. Results show that PM concentration was reduced by 37% to 51% in the treatment section of the CF hen house. The lower reduction efficiency in the field experiment than in the lab-scale tests was partially attributed to the fact that water spray in the commercial hen house was applied only to the open litter area, and not the litter area under the aviary system, due to limited space. Adjusting the spray dosage according to litter depth is necessary for maintaining an appreciable reduction efficiency. Litter moisture content in the treatment section was 9% to 14% higher than in the control section (15.6% vs. 14% in trial 1, 14.6% vs. 12.2% in trial 2, and 17.7% vs. 14.9% in trial 3), but NH3 concentrations in the treatment and control sections were similar during the field experiment. Keywords: Air quality, Alternative hen housing, Dust, Litter moisture content.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=2310&context=abe_eng_pubs

Adriano Pérez-Bonilla

Papers

Air disinfection in laying hen houses: effect on airborne microorganisms with focus on Mycoplasma gallisepticum.