Institution: Georgia Institute of Technology
Spyros G. Pavlostathis
Georgia Institute of Technology
School of Civil and Environmental Engineering
Atlanta, GA 30332-0512
|Peracetic acid (PAA) has been an effective antimicrobial agent in the poultry industry used predominantly in chillers. Recently, its use has been expanded to other unit processes as well. Residual PAA (PAA remaining after its reaction with wastewater constituents) may impact biological wastewater treatment processes, thus making it hard to meet effluent discharge requirements. Because of potential negative impacts on effluent quality and the rapidly increasing use of PAA in poultry processing plants, more detailed information relative to the fate and effect of PAA in poultry processing wastewater treatment systems is needed.
The overall goal of this project was to systematically assess the fate and long-term effect of PAA solutions on poultry processing biological nitrogen removal (BNR) and anaerobic treatment processes typically used by the poultry processing industry and develop an effective methodology to either avoid or mitigate any negative effects.
This research project undertook the following tasks: 1) Assessment of the long-term effect of PAA and Hydrogen Peroxide (H2O2 ) on the performance of a continuous-flow, bench-scale BNR system (anaerobic-anoxic-aerobic reactors in series with internal recycle); 2) Bench-scale assessment of the long-term effect of PAA and H2O2 on anaerobic, mixed fermentative/methanogenic processes; 3) Evaluation of the diversity and stability of microbial communities in both the BNR and anaerobic systems in response to a range of PAA/H2O2 concentrations, as well as their recovery in affected systems; 4) Development of effective methodologies to either avoid or mitigate any negative effects of PAA solutions on biological treatment systems.
Some of the key findings of the project showed that continuous, direct addition of PAA solution up to 200/29 mg/L PAA/H2O2 (feed-based concentration) to the BNR anaerobic reactor did not affect system performance. Both processes were negatively affected by continuous feeding with residual PAA-bearing wastewater, leading to complete system collapse at 200 mg/L residual PAA. The effect of PAA on system performance was fast reversed and not lasting after feeding with PAA-free wastewater. The microbial community composition in the three BNR system reactors shifted significantly over the long-term operation with addition of PAA solution, but the PAA impact was fast reversed after PAA addition was ceased. Nitrification, denitrification and anaerobic degradation will be affected when wastewater with high residual PAA concentrations are expected at the end of the plant operation shift due to emptying of chiller tanks, or in the case of accidental PAA solution spills.
This study quantified the long-term effect of PAA/H2O2 on the treatment efficiency of biological aerobic, nitrifying, denitrifying and anaerobic degradation processes. Such information enhances our understanding relative to the fate and effect of PAA solutions in poultry processing wastewater treatment systems, information crucial for the rational design and operation of biological treatment processes, especially those related to biological nutrient removal and anaerobic wastewater treatment. The outcome of the present study provides systematic information to the poultry processing industry to develop a sound methodology and employ measures that will ensure the continuous use of PAA solutions to achieve pathogen-free products, while avoiding upsets of biological wastewater treatment processes by PAA-bearing wastewater.