Impact of scalding duration and scalding water temperature on broiler processing wastewater loadings

Abstract

Three experiments were performed to evaluate scalding tank poultry processing wastewater (PPW) loading following the slaughter and scalding of commercially raised broilers: hard vs. soft scalding protocols (experiment 1), scalding immersion time and temperature individually (experiment 2), and the presence of residual blood (experiment 3). One-liter water samples were taken from each scald tank and analyzed for chemical oxygen demand (COD), total solids (TS), and total suspended solid (TSS) concentrations, which were then used to calculate PPW loading (g/kg broiler live weight). For experiment 1, there was significantly higher PPW loading for soft scald/tank 1 (1.834 g/kglwt) than hard scald/tank 1 (1.510 g/kglwt) protocol for COD. There were no other significant differences between scalding protocols for experiments 1 and 2, but there was a trend that the longer immersion time protocols resulted in PPW higher loading for all 3 analytics. For all 3 experiments, the use of sequential scalder tanks significantly reduced PPW loading for both organic and solid materials (COD, TS, and TSS) with tank 1 being significantly higher (50 to 89%) than tanks 2 and 3. Residual blood following a 120 s bleed time did not impact PPW loading compared to non-bled carcasses. These results indicate that scalder immersion time appears to be major indicator for predicting PPW loading in scalders and shows decreases with each sequential scald tank.