Abstract
One of the prerequisites for sustainable development is integrated waste
management, including sewage sludge. Besides its good fertilization
properties, sewage sludge, which is an inevitable by-product of sewage
treatment, accumulates toxic chemical substances and dangerous pathogenic
and toxicogenic organisms. Uncontrolled introduction of sewage sludge into
soil might pose a serious threat to food chain and natural soil
microflora. This in effect might disturb the ecological balance in a
particular ecosystem. This study presents author’s own investigations of
the sanitary conditions of sewage sludge and the conditions after the
processes of aerobic and anaerobic stabilization. The investigated sewage
sludge originated from a municipal wastewater treatment plant. The sewage
sludge samples were transferred onto proliferation and diagnostic media.
The results of the analysis obtained in this study confirmed that sewage
sludge is a material which is rich in microorganisms, including pathogenic
bacterial species such as: Escherichia coli and Salmonella typhimurium.
Mycological tests demonstrated that sewage sludge is a material which is
conducive to proliferation of yeast-like and mould-like fungi, among which
both pathogenic and toxinogenic species can be present. Quantitative
analysis of the investigated sewage sludge demonstrated that the processes
of stabilization reduce the content of microorganisms but they do not
guarantee product safety in sanitary terms. A huge variability and variety
of biological composition points to the need for further research in the
field of sanitary characteristics of sewage sludge and survival rate in
microorganisms from different types of sewage sludge.
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