REDUCTION OF PARTICULATE MATTER AND AMMONIA BY SPRAYING ACIDIC ELECTROLYZED WATER ONTO LITTER OF AVIARY HEN HOUSES : A LAB-SCALE STUDY

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, PM_2.5, 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 < 0.05). The results suggest that a 25 mL kg^-1 dry litter d^-1 dosage at pH 3 is a prudent combination to control PM levels without causing undesired elevation in NH₃ emissions in litter-based cage-free aviary hen houses. This lab-based finding provides the basis for field verification testing.