Date of Award

Spring 2003

Project Type

Dissertation

Program or Major

Microbiology

Degree Name

Doctor of Philosophy

First Advisor

Aaron B Margolin

Abstract

The use of lime to reduce or eliminate pathogen content is a cost-effective treatment method currently being employed in many Class B biosolids production plants in the United States. A bench scale model of lime stabilization was designed to evaluate pathogen persistence. The survivability of poliovirus type 1, fecal coliforms, Salmonella, adenovirus type 5, rotavirus Wa, and the male-specific bacteriophage MS-2 was evaluated under lime stabilization conditions in various matrices. Salmonella and fecal coliforms were evaluated at 28°C and poliovirus and MS-2 were evaluated at both 28°C and 4°C for survivability under lime stabilization conditions in a sludge matrix. All microorganisms evaluated were discovered to be below detectable levels following twelve hours of liming for all temperatures evaluated. Adenovirus type 5, rotavirus Wa, and MS-2 were evaluated in water, biosolids, previously limed and raw sludge and biosolids matrices at 28°C and 4°C. In all matrices evaluated, adenovirus type 5, rotavirus Wa and MS-2 were below detectable levels following a twenty-four hour incubation with lime, with inactivation rates varying depending on the sample matrix evaluated.

Evaluation of reliable and cost effective treatment processes to demonstrate sufficient inactivation of pathogens provides valuable information for implementation of treatment technologies. This research has demonstrated that lime stabilization is effective at reducing fecal coliforms and Salmonella in a sludge matrix at 28°C, poliovirus in a sludge matrix at 28°C and 4°C, and adenovirus type 5, rotavirus Wa and male-specific bacteriophage in sludge and biosolids matrices at 28°C and 4°C when calcium hydroxide was added to achieve a pH of 12 for 2 hours and 11.5 for 22 hours. The similar inactivation of MS-2 under lime stabilization conditions, and prevalence and ease of recovery in sludge samples, combined with the need for a representative indicator in the absence of adequate methodology for recovery and detection of enteric viruses in sludge and biosolids makes male specific bacteriophages a suitable indicator as an index for enteric viruses, to be used for the monitoring of biosolids to determine treatment effectiveness following lime stabilization.

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