Researchers Take a Closer Look at the Impact of Sanitizing Chemicals on Wastewater Treatment Systems

In early 2007, after a relatively long period of sustained low temperatures, a number of poultry processing facilities in the U.S. Southeast experienced increased ammonia levels in effluent wastewater. These facilities all employed biological treatment processes for nitrogen, and in some cases, phosphorus removal. Limited analysis and testing with wastewater samples collected at one plant showed that the nitrification process upset was caused by sustained low temperatures (below 15 °C) and more than likely exacerbated by the presence of disinfectants in the waste stream.

overline screening/sorting prototype system

Ulas Tezel, Ph.D. student in the Environmental Engineering Group at the Georgia Tech School of Civil and Environmental Engineering, tests a wastewater treatment process effluent for quaternary ammonium compounds using a method developed as part of research funded by the U.S. Poultry & Egg Association.

These events point out that although product quality and safety are paramount in the poultry industry, intervention treatments used to control foodborne pathogens can cause upsets downstream in the effluent pretreatment area. Optimizing in-plant disinfection with wastewater treatment is more challenging in that chemistries designed to disinfect foodborne pathogens can also impact useful wastewater treatment bacteria.

Ongoing research at Georgia Tech indicates that the chemistries of selected quaternary ammonium compounds (QACs or QUATs), which are generally regarded as safe (GRAS) sanitizers, can present significant difficulties for biological wastewater treatment systems under certain conditions.

QACs are common ingredients of sanitation solutions used extensively by the food processing industry to clean food contact surfaces. QACs are a favored antimicrobial because they are cationic and tend to bind with biological, organic, and other negatively charged substances; are water soluble; stable and breakdown slowly; provide antiseptic, disinfectant, and sporostatic activity; tend to be more effective than chlorine-based chemistries and other biocides in the presence of moderate amounts of organic matter; generally are safe for users; and are relatively inexpensive. Washing and other activities that rely on these solutions during food processing result in QACs-bearing wastewater. And their impact can go beyond plant wastewater treatment systems as QACs can also be problematic for publicly owned treatment works (POTWs), especially for processes such as nitrification and anaerobic digestion.

“Widespread research regarding the sources of poultry product foodborne pathogenic contamination indicates that intervention may require strategies that go beyond the processing plant,” says John Pierson, a principal research engineer in Georgia Tech’s Food Processing Technology Division and head of the division’s Food Safety, Environment, and Energy Technology Group.

Hazard Analysis and Critical Control Point (HACCP) programs in all U.S. meat and poultry processing plants under federal inspection are designed to eliminate or manage food safety hazards; additional federal requirements mandate the testing of the poultry processing plant environment and carcasses for the presence of the foodborne pathogen Salmonella along with generic E. coli. However, explains Pierson, a growing body of work indicates that on-farm pathogen reduction programs by poultry integrators (i.e., hatchery, feed mill, breeder, and grow-out operations) may be necessary in order to successfully meet required federal and state processing plant pathogen control targets.

For in-plant treatments, a variety of chemistries for disinfection and sanitation are available, including chlorine-based compounds (e.g., hypochlorous acid, chloramines, and chlorine dioxide), peroxyacetic acid, acidified calcium sulfate, acidified sodium chlorite, and trisodium phosphate. QACs are primarily used for equipment surface sanitation (e.g., QACs are applied to equipment at 200 ppm for up to 24 hours to combat increased concerns about Listeria), although cetylpyridium chloride (CPC) and other selected QACs are used on carcasses and egg surfaces, respectively. Pierson notes that foodborne pathogen intervention strategies for poultry products and on-farm activities are similar.

Steven Woodruff with Woodruff & Howe Environmental Engineering (WHEE), Inc. has worked on a number of projects related to wastewater treatment system upsets, where QAC usage at a food processing plant was identified as a potential contributing factor to these problems.

Woodruff notes that the QAC analytical testing method developed by Georgia Tech has significantly aided in the assessment of potential wastewater impacts from QAC usage as well as allowed for development of remedial action plans when required.

“The analytical methods commonly used for QAC analysis can result in erroneous results due to interferences and other problems associated with these analytical methods. These problems have been significantly eliminated in the QAC method developed by Georgia Tech, which has been a tremendous benefit for various food producers in Georgia. Georgia Tech researchers have also provided significant assistance in associated investigations,” says Woodruff.

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Food Processing Technology Division
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Angela Colar - Editor -