EVALUATION OF THE TOXICOLOGICAL RISK ASSOCIATED WITH THE USE OF POLYACRYLAMIDES IN THE RECOVERY OF NUTRIENTS FROM FOOD-PROCESSING WASTE-(I)

Trivalent metal ions such as iron and aluminum are currently employed to flocculate liquid-borne solids from food-processing waste streams. These captured nutrient-rich waste solids are disposed of mainly throu gh land applications (e.g., subsoil injection) because of the potentia l toxicity associated with the metal salts. Low-toxicity, water-solubl e polyacrylamide polymers are currently approved for and employed as f locculants in potable water applications. The use of these polymers in food-processing waste streams could enable the captured solids to be recycled as components of animal feed, thus decreasing the burden on l andfills and making good use of the proteinaceous matrix. However, pol yacrylamides contain very low concentrations of acrylamide monomer, wh ich is highly toxic and can cause neurotoxicity, cytogenic lesions, an d an increase in tumor rates in experimental animals. With use of two industrial food processing wastes, experiments were conducted to deter mine how acrylamide monomer would partition during a solids/liquid sep aration and subsequent rendering. Based on the analytical data, 96% of the acrylamide monomer was measured in the water portion after separa tion. Because of background interferences, acrylamide could not be dir ectly measured in the solids portion. With use of these results and wo rst-case calculations, <2 ppb of acrylamide could be present in animal feed, thereby making the associated risk de minimis.