Most people consider sewage sludge an unpleasant by-product of civilization and a worthless, problematic waste. However, this is not the case for several researchers.
In the professional world, it is an established fact that, in addition to a number of inorganic substances, sewage sludge also contains many bacteria that include protein.
With the growing significance of closed substance cycle waste management, the scientific focus also seems to be on these substances. Examinations of the excess sludge of biological sewage treatment were conducted, where bacteria are mainly contained.
Characteristics of Bacteria
The professional world divides bacteria into many different groups; for example, based on their behavior during the Gram stain technique. A common feature of bacteria is that they protect themselves with a solid cellular wall.
At the University of Applied Sciences in Merseburg, Germany, the destruction of cellular walls was examined for the thesis of Mr Michael Herrmann, under the guidance of Prof. Dr. Winkler, University of Applied Sciences, Merseburg and Dr. Schaffer, IVG mbh Schkopau.
The recovery index was designated as a dimension for the decomposition. For this, the concentration of protein during the solid phase was established much earlier as a reference value. Examination of different decomposition methods was conducted in the laboratory.
Mechanical Decomposition Methods to be Mentioned
- Homogenizer ULTRA-TURRAX T25, IKA laboratory equipment
- Ultrasonic Homogenizer SONOREX RK 1028 CH, BANDELIN electronic GmbH
- Planetary Mono Mill PULVERISETTE 6 classic line, FRITSCH milling and sizing
The chemical procedure used was acid hydrolysis. A protein assay was conducted for the characterization of the effectiveness of the decomposition.
Preparation with the Planetary Mill
Dry matter contents of approximately 10, 20 and 40 g/l were examined in the planetary mill. Glass pearls of 0.4 to 0.6 mm diameter were utilized as a grinding medium.
The grinding medium’s volume amount was matched 1.1 to the liquid volume. Treatment times of 2, 5 and 10 minutes were analyzed.
In principle, it was established that the recovery index rises with increasing processing duration and a decreasing of the dry matter contents. The fact that samples processed with the Planetary Mono Mill PULVERISETTE 6 classic line have the highest recovery index was revealed through the comparative observation of the decomposition methods.
This information has been sourced, reviewed and adapted from materials provided by FRITSCH GMBH - Milling and Sizing.
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