Evaluating viral inactivation in the liquid waste stream from a viral total nucleic acid extraction kit for safe disposal

Safe laboratory processing requires mitigating risks from the release of pathogens into the environment through generated waste streams. This study evaluated the inactivation kinetics of bacteriophage MS2 as a surrogate for infectious viruses in liquid waste produced from total nucleic acid extractions of wastewater. The goal was to determine a waste handling protocol that ensures sufficient viral infectivity loss (i.e., inactivation) for safe disposal. Liquid waste was generated using a viral total nucleic acid extraction kit (Wizard® Enviro Total Nucleic Acid Kit, Promega, The United States of America) containing guanidinium chloride, isopropanol, ethanol, and other residual reagents. MS2 phage was artificially added into liquid waste, and inactivation was monitored over 24 h using double agar layer plaque assays. A one-phase exponential decay model was applied to estimate the time required for safe disposal, showing MS2 inactivation followed an exponential decay pattern, achieving a predicted 6-log₁₀ reduction at an average of 2.41 h (145 min), with a 95 % confidence interval of 1.34 h (80 min) to 4.05 h (243 min). However, only the 24-hour holding time was observed to significantly exceed the 6-log₁₀ reduction threshold, supporting its recommendation as a conservative and practical holding time after which the waste can be safely disposed of as chemical solvent waste without additional decontamination measures such as autoclaving, as viral infectivity is reduced by at least 6-log₁₀.