Inactivation of adenovirus type 5, rotavirus Wa and male specific coliphage (MS2) in biosolids by lime stabilization

Abstract

The use of lime to reduce or eliminate pathogen content is a cost-effective treatment currently employed in many Class B biosolids production plants in the United States. A bench scale model of lime stabilization was designed to evaluate the survival of adenovirus type 5, rotavirus Wa, and the male specific bacteriophage, MS2, in various matrices. Each virus was initially evaluated independently in a reverse osmosis treated water matrix limed with an aqueous solution of calcium hydroxide for 24-hr at 22 +/- 5 degrees C. In all R/O water trials, adenovirus type 5, rotavirus Wa and MS2 were below detectable levels (<100.5 TCID50/mL and <1 PFU/mL respectively) following 0.1-hr of liming. Adenovirus type 5, rotavirus Wa, and MS2, were inoculated into composted, raw and previously limed matrices, representative of sludge and biosolids, to achieve a final concentration of approximately 104 PFU or TCID50/mL. Each matrix was limed for 24-hr at 22 +/- 5 degrees C and 4 +/- 2 degrees C. In all trials virus was below detectable levels following a 24-hr incubation. The time required for viral inactivation varied depending on the temperature and sample matrix. This research demonstrates reduction of adenovirus type 5, rotavirus Wa, and male-specific bacteriophage, in water, sludge and biosolids matrices following addition of an 8% calcium hydroxide slurry to achieve a pH of 12 for 2-hr reduced to 11.5 for 22-hr by addition of 0.1 N HCl. In these trials, MS2 was a conservative indicator of the efficacy of lime stabilization of adenovirus Type 5 and rotavirus Wa and therefore is proposed as a useful indicator organism.

Figure 1:

Average adenovirus type 5 and MS2 inactivation in sludge matrices (compost, raw and previously limed) lime stabilized at room temperature (22 ± 5°C).

Figure 2:

Average adenovirus type 5 and MS2 inactivation in sludge matrices (compost, raw and previously limed) lime stabilized at reduced temperature (4 ± 2°C).

Figure 3:

Rotavirus Wa and MS2 persistence in a test lime and control RO water matrix at room temperature (22 ± 5°C).

Figure 4:

Average rotavirus Wa and MS2 inactivation in sludge matrices (compost, raw and previously limed) lime stabilized at room temperature (22 ± 5°C).

Figure 5:

Average rotavirus Wa and MS2 inactivation in sludge matrices (compost, raw and previously limed) lime stabilized at reduced temperature (4 ± 2°C).