Culturability of potential pathogenic bacteria in a co-digestion anaerobic digester system
File(s)
Date
2018-01-31Author
Johnson, Shannon
Advisor(s)
Kleinheinz, Greg
Metadata
Show full item recordAbstract
Anaerobic digestion (AD) has the potential to reduce organic wastes and produce
renewable energy from the degradation of organic materials to produce biogas. However,
mixed substrate anaerobic digesters may create a suitable environment for opportunistic
pathogenic bacteria. The fate of potential bacterial pathogens has been studied in manure-based digesters but their survival is not well understood when digesters are co-fed with
food waste. Mixed substrates may change internal conditions and subsequently pathogen
survival, resulting in concerns for general environmental health. The purpose of this
study was to introduce and enumerate potentially pathogenic bacteria in a bench-scale
AD system while analyzing possible relationships between colony growth with typical
AD parameters: temperature, pH, and volatile fatty acids (VFAs). Food waste was
utilized as a substrate and percolate (a manure surrogate) was used as an inoculum to
examine the survival of five species of bacteria (Campylobacter jejuni, Staphylococcus
aureus, Salmonella enterica, Enterococcus faecalis, and Escherichia coli) that were
selected on likelihood of entering a digester or that they are indicators for groups
potentially located in digesters. It is hypothesized that incomplete acidogenesis – from
mixed substrates – may increase VFAs, lower pH, and therefore decrease pathogen
survival. A modified membrane filtration method, with selective and differential media,
were used to enumerate the microorganisms. In the Enterococcus spp. experimental
growth system, linear regression analyses revealed that there is a relationship of colony
reduction with: temperature, pH, and total VFAs. The reduction of four of the five
organisms, early in AD, indicates that co-fed digesters can reduce pathogens and lower
environmental health risks.
Subject
Biogas
Anaerobic bacteria--Growth
Permanent Link
http://digital.library.wisc.edu/1793/77922Description
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science of Biology