148 Evaluating water characteristics and their effects on reducing water pH using citric acid

Abstract The goal of this experiment was to identify water characteristics that affect the ability to reduce pH when using water acidifiers. A total of 27 water samples from swine operations across the Midwest were collected and pH, Ca, and Mg were analyzed. Total hardness was calculated as the combined values of Ca and Mg and expressed in mg of CaCO3/L. Hardness values ranged from 142 mg CaCO3/L to 644 mg CaCO3/L, with an average hardness of 375 mg CaCO3/L. Initial sample pH ranged from 7.52 to 8.47 with an average value of 8.05. In triplicates, 10 mL of water from each source was titrated with citric acid (Citrasol Stock Booster, Northwest Livestock Distribution, Medina, MN) to reach a pH target of 5.0, 4.5, and 4.0 ± 0.05. The effects of individual characteristics were analyzed in R using the lm function to determine linear and quadratic relationships between water measurements and the amount of acid required to reach the target pH. As initial sample pH increased, a linear decrease in the amount of acid to reach the target pH of 4.0 was observed (P = 0.014, R2= 0.158). A significant but weak relationship (P = 0.016, R2= 0.179) between hardness and the amount of acid required to reach a pH of 4.0 was observed, where increasing hardness linearly increased the amount of acid required to reach a pH of 4.0. The quantity of Ca within the water source linearly increased (P = 0.023, R2= 0.159) the amount of acid required to reach a pH of 4.0 and a tendency for a quadratic relationship (P = 0.070, R2= 0.238) was also observed between Ca concentration of the water source and the amount of acid to reach a pH of 4.0. Magnesium concentrations also tended to linearly increase the amount of acid required to reach a final pH of 4.0 (P = 0.057, R2= 0.103). Titrating to either a pH of 5.0 (P < 0.001, R2 = 0.974) or 4.5 (P < 0.001, R2 = 0.990) also will predict the amount of acid required to reach a pH of 4.0. In conclusion, water hardness, Ca, Mg, and initial pH do not fully predict the amount of acid required to reduce water samples to a target pH of 4.0; however, weak relationships were observed that can partially explain the variation in acid requirements. These data suggest that acid titrations of water samples are required and should be site specific to establish an estimate for how much acid is required to reach a water pH of 4.0.