Analysis of the Impact of Factors Affecting Survivability of Bacteria from the Enterobacteriaceae Family during Sewage Sludge Composting
Agnieszka Wolna-Maruwka
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Department of General and Environmental Microbiology, University of Life Sciences in Poznań,
Szydłowska 50, 60-656 Poznań, Poland
Pol. J. Environ. Stud. 2012;21(3):771-781
The objective of the performed investigations was to assess the influence of the value of temperature, pH, gas emissions, and doses of BAF microbiological inoculum on the reduction or total elimination of bacteria from the Enterobacteriaceae family.
The performed experiment consisted of two stages. In the course of the first trial, sewage sludge was subjected to composting together with straw and sawdust in a cybernetic bioreactor. The experimental design included three treatments, two of which were inoculated twice with BAF inoculum: K1 – control, compost without inoculation; K2 – compost+1500 ml BAF; K3 – compost+750 ml BAF.
The BAF (Bacteria-Actinomycetes-Fungi) inoculum was designed at the Department of General and Environmental Microbiology of Poznań University of Life Sciences and was made up of bacterial strains, actinomycetes, and mould fungi isolated from mature compost.
The microbiological analyses applied in this experiment involved determination of total counts of bacteria belonging to the Enterobacteriaceae family using, for this purpose, Koch’s plate method followed by biochemical tests confirming species membership of the above-mentioned bacteria.
In the second part of the experiment, bacteria from Escherichia, Klebsiella, and Citrobacter genera isolated from mature composts were subjected to the ring method with the aim of examining mutual interactions between the above-mentioned bacterial species and the BAF inoculum.
On the basis of the obtained research results, it was found that the recorded reduction in numbers of the discussed microorganisms was caused by physico-chemical factors of the composting process, especially by the inoculation of biowastes by the BAF biopreparation.
The performed in vitro analysis of interactions between the Escherichia coli, Citrobacter freundii, and Klebsiella pneumoniae strains and the applied BAF inoculum revealed considerable sensitivity of the above strains to the experimental biopreparation.
However, in in vivo conditions, E. coli bacteria exhibited resistance to the action of the above dose of the inoculum. Therefore, continuation of the above investigations appears necessary.
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