Technical Abstract: Developing food safety intervention technology that can be readily adopted by the industry often requires test conditions that match as closely as possible to those of commercial food processing operations; yet biosafety risks inherent in pathogen studies constrain most experiments to laboratory settings. In this study, we report the first semi-commercial pilot-scale evaluation of a new process aid, T128, for its impact on enhancing the antimicrobial efficacy of chlorinated wash water against pathogen survival and cross-contamination. A non-pathogenic, BSL-1, strain of E. coli O157:H7 was inoculated onto freshly harvested baby spinach leaves and washed with large amounts of freshly cut un-inoculated iceberg lettuce shreds in chlorinated wash water, in the presence or absence of T128. The use of T128 did not significantly (P > 0.05) influence the rate of wash water deterioration, particularly the increase of organic matter accumulation or the decrease in free chlorine levels, during washing. However, in the absence of T128 (Control), survival of E. coli O157:H7 in wash water and cross-contamination of un-inoculated lettuce frequently occurred when free chlorine in solution dropped below 1 mg/L during the wash process. In contrast, use of T128 significantly reduced the occurrence of E. coli O157:H7 surviving in wash water and of cross-contamination to un-inoculated shredded iceberg lettuce under the same operational conditions. No significant difference was observed in E. coli O157:H7 populations remaining on spinach leaves after washing in chlorinated water in the presence or absence of T-128. Although the mechanism of the synergistic interaction between T128 and free chlorine is still unclear, application of this novel wash aid in a chlorine-based fresh produce sanitization system could increase the safety margin of process control on commercial fresh-cut operations.