The microbiological characteristics of effluent in poultry processing plants

Abstract

In this study selected microbiological characteristics of effluent from poultry processing plants were evaluated. Results indicate that 75% of the total plant effluent is discharged during the regular processing period and the remaining 25% is discharged during periods of clean-up and minimum plant activity. Microbial concentrations in the final plant effluent remained at elevated levels during the processing and further-processing periods, decreased gradually during the clean-up period and reached minimal levels during normal down-time. Although microbial numbers in the scalding and chilling systems were somewhat controlled by the high and low temperatures and the continuous overflow, significant numbers of bacteria were discharged from these operations into the final plant effluent. More than 60% of total plant effluent was discharged from the defeathering and offal collecting operations. About 95% of the total bacterial discharge was contained in this combined effluent. To reduce bacterial loading of the plant effluent, it is suggested that the effluent discharged from these two functional operations be treated prior to discharge to the final effluent flow. This procedure can potentially remove almost all of the bacterial discharge by treating only 60% of the total effluent volume. Under commercial processing conditions, bacterial and biochemical pollutants in the scald system increased continuously during a four hour processing period. During this test period, the cleaning efficiency of the scald water remained relatively constant and removed about 85% of surface bacteria from the test carcasses. In laboratory trials, post-scald bacterial counts on broiler thighs were directly associated with bacterial numbers on pre-scald thigh surfaces. Scald water with excessively high bacterial numbers contaminated broiler thighs which contained relatively low numbers of microorganisms pre-scald. No change in cleaning efficiency was noted with "normal" bacterial concentrations in the scald water and on the broiler thigh surfaces.