Date of Award

Winter 2003

Project Type

Dissertation

Program or Major

Microbiology

Degree Name

Doctor of Philosophy

First Advisor

Aaron Margolin

Abstract

The management of biosolids in the United States has become an issue of public health concern in regard to disposal. Congress created the Clean Water Act in 1972 to protect waters in the United States and as a result, no longer can human waste be dumped into oceans or rivers. Means of disposal of biosolids are focused on land application today. The practice of land application takes into consideration the classification of the biosolids material and management practices to control access to and growth of crops on the land. Biosolids are classified as either Class A or Class B depending on which process was used to produce the material. Class A biosolids are "virtually" pathogen free and Class B have pathogens present in reduced numbers.

The only parasite indicator organism that is required by the Environmental Protection Agency's Part 503 Rule to screen for in biosolids is Ascaris lumbricoides. Protozoans including Cryptosporidium parvum and Giardia lamblia were not considered human pathogens when the Part 503 rule was written, but are present in biosolids materials using the recovery methods developed in this project. Through the use of these methods, the protozoa were found to be at least as prevalent as Ascaris lumbricoides. A. lumbricoides cannot be used as an indicator of the presence of all parasites since it has a variable geographic distribution in the United States.

Two biosolids treatment methods were assessed to determine the persistence of parasites in Class B lime stabilization and Class A composting. Results of the lime stabilization procedure show evidence that this method is effective in reducing bacteria concentration, but that the parasites persisted throughout the treatment process. The Class A treatment process, on the other hand, was effective in reducing C. parvum, G. lamblia and A. lumbricoides.

The Class A composting process involves heat inactivation and is a method that has shown to reduce pathogens more effectively than Class B treatments where no heat is required. The ability to demonstrate that pathogens are reduced after a particular treatment is dependent on the availability of efficient recovery methods and viability/infectivity assays.

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