Document Type Doctoral Thesis Author Chale-Matsau, Jacobeth Raesibe Bettina URN etd-09292005-114114 Document Title Persistence of Human Pathogens in a Crop Grown from Sewage Sludge Treated Soil Degree PhD (Water Utilisation) Department Chemical Engineering Supervisor
Advisor Name Title Dr H G Snyman Keywords
- management practice
- low metal sludge
- high metal sludge
- risk assessment
- sewage sludge
Date 2005-06-13 Availability unrestricted AbstractThe advantages associated with the use of sewage sludge in agricultural land have motivated many countries to use sewage sludge for soil amendment purposes. South Africa’s deteriorated agricultural soil could benefit from this nutritional and cost effective product. However, the major shortcoming of sewage sludge is the presence of various pathogenic microorganisms. This raised concern amongst researchers with regard to public safety. The focus of this study, was to investigate the prevalence of pathogens in a crop grown in soil enriched with sewage sludge and to determine risk of infection thereof and to suggest appropriate management practice for sewage sludge use.
Potato (Solanum tuberrosum), which is a high risk crop was used, to simulate a worst case scenario. Both the low metal sludge (LMS) and high metal sludge (HMS) were found to have associated diverse numbers of bacteria. Using culture-based technique, E.coli and Salmonella spp were found to persist in soil throughout the experimental period. One treatment option (LMS 16 tons/ha) showed a prevalence of these microorganisms in potatoes.
Subsequent molecular studies based on amplification of 16S rRNA gene, yielded limited contamination of potatoes with enteric pathogens, however diverse types of opportunistic, pathogens (mostly environmental pathogens) were isolated from the potatoes. Enteric pathogens were isolated from the sewage treated soil in which these potatoes were grown.
This study has indicated that growing even high risk crops, may lead to limited infestation of produce with primary pathogens. However, proper treatment of sewage sludge prior to use in agriculture is recommended to ensure public safety.
The management requirements indicated in this study serve as recommended actions that can be implemented to ensure human safety with regard to sludge application to agricultural land.
Filename Size Approximate Download Time (Hours:Minutes:Seconds)
28.8 Modem 56K Modem ISDN (64 Kb) ISDN (128 Kb) Higher-speed Access 00front.pdf 46.54 Kb 00:00:12 00:00:06 00:00:05 00:00:02 < 00:00:01 01chapter1.pdf 32.34 Kb 00:00:08 00:00:04 00:00:04 00:00:02 < 00:00:01 02chapter2.pdf 156.86 Kb 00:00:43 00:00:22 00:00:19 00:00:09 < 00:00:01 03chapter3.pdf 72.31 Kb 00:00:20 00:00:10 00:00:09 00:00:04 < 00:00:01 04chapter4.pdf 84.62 Kb 00:00:23 00:00:12 00:00:10 00:00:05 < 00:00:01 05chapter5.pdf 164.56 Kb 00:00:45 00:00:23 00:00:20 00:00:10 < 00:00:01 06chapter6.pdf 100.61 Kb 00:00:27 00:00:14 00:00:12 00:00:06 < 00:00:01 07chapter7.pdf 55.81 Kb 00:00:15 00:00:07 00:00:06 00:00:03 < 00:00:01 08chapter8.pdf 29.41 Kb 00:00:08 00:00:04 00:00:03 00:00:01 < 00:00:01 09appendices.pdf 44.26 Kb 00:00:12 00:00:06 00:00:05 00:00:02 < 00:00:01