Effects of Free and Complexed Quaternary Ammonium Surfactants on Aerobic Wastewater Treatment Processes Treating Poultry Processing Wastewater

Due to their biocidal properties, quaternary ammonium compounds are widely utilized by the poultry production and processing industry to kill pathogenic bacteria. As most of these compounds are slowly bio-degraded, if at all, they eventually wind up in the wastewater from these plants. These compounds are used as biocides because they efficiently kill bacteria, so it is not surprising that they inhibit the metabolism of aerobic wastewater treatment processes. Seventy three percent or 26 poultry wastewater sample tested had detectable concentrations of quaternary ammonium surfactants. A variety of quaternary ammonium species were detected in the samples, with cetyl pyridinium chloride being the most common, followed by several benzalkonium species. The relationship between quaternary ammonium surfactants and biomass inhibition was assessed by measuring the metabolic indicator adenosine tri phosphate (ATP). Reductions in ATP formation rate indicate inhibition of the biomass. The ability of using total QACs to predict the potential for poultry wastewater treatment process inhibition is not good. Differences in partitioning between solids and the more bio-available free-form skewed the response and would make predictions less accurate. Free QAC measurements do a much better job of predicting the inhibition of an aerobic poultry wastewater treatment process. There is approximately a 10 percent reduction of biomass metabolism for every mg/L of free-QAC present. While the correlation is much better than for total QACs, there was still a large degree of variability