Effects of freezing and storage temperature on MS2 viability

Monitoring human enteric virus levels in domestic wastewater effluent is crucial to protecting human health. Occasionally, during intensive sampling, wastewater samples must be stored for later viral analysis. Little data exist regarding how enteric viruses survive during storage at different temperatures in secondary treated wastewater. During a field-scale study assessing pathogen removal performance by various onsite treatment technologies, the MS2 bacteriophage, an indicator of enteric viruses, was inoculated into septic tank (STE), sand filter, peat filter and constructed wetland (CW) effluents to determine virus decay at various storage temperatures. Virus stored at temperatures ≥10°C and at -20°C decayed nearly twice as fast as those stored at 4°C or -80°C. Decreased water quality decreased viral decay rates at 4°C and -80°C, with slowest decay occurring in STE and the fastest in sterile PBS and low pH peat effluent. In CW effluent after 8 days, less MS2 was inactivated when stored at 4°C (20%) compared to -80°C (58%); however, during extended storage (∼300 days), less MS2 was inactivated at -80°C (75%) compared) to 4°C (93%). We recommend that viruses in wastewater be stored in the dark at 4°C unless storage for >40 days is necessary.