Sewage Sludge Treatment
Sewage sludge is produced by sedimentation after treatment of waste water. It is often used as an agricultural fertiliser due to its high nitrogen and phosphate content.
This practice is being reduced significantly in Germany due to strict legislation, as sewage sludge contains harmful substances which become dispersed and accumulate in the ground. As a preventative measure, only high-quality sewage sludge is still used in agriculture. The rest is incinerated and used in energy production. However, hazardous substances can also be released when sludge is burnt in power stations and cement plants.
Developed and tested technical solutions for environmentally friendly usage and disposal of sewage sludge include:
• treatment (drying),
• re-use (agriculture) and
• combustion (emissions and energy yield).
This study involved the evaluation of various disposal options in terms of their environment-friendliness, cost-effectiveness and state-of-the-art technology for each method considered. Results obtained will allow political decision-makers in particular to provide a scientific basis for their selection of a specific disposal option.
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In a two-stage anaerobic plant using the Schwarting-Uhde process, it has been demonstrated that the biological treatment of organic wastes, even residual wastes, represents an economical and ecologically sound alternative to disposal by combustion. Process residues are suitable for landfill, on the grounds of their low level of respiratory activity.
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A local waste-management concept plans the common digestion of bio waste and sewage sludge for the generation of fermentation gas and production of a compostable residual sludge. To this end the separately collected bio waste was pre-treated in a material dissolver and putrefied together with sewage sludge in the already existing digester.
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Cost and energy savings associated with the application of high-performance digestion, with demonstrable transferability to other municipalities and sewage treatment plants
The incorporation of a high-capacity stage, based upon the principle of the Schwarting-Uhde process, into an existing sludge digestion installation has resulted in stable operation, associated with higher biogas production, improved degradation rates and reduced operating costs. Results obtained are effectively transferable to other sewage treatment plants handling different sewage sludges.
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This investigation demonstrates that this process is capable of decontaminating municipal and, to a limited extent, industrial sludges to a degree where they will be suitable for agricultural use. A combination of this process with an abbreviated upstream digestion stage has also proved to be highly promising.
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Keywords:
Klärschlamm, Abbau, Schlammbehandlung, Schadstoff
More keywords
, Polychlorbiphenyl, Verfahrenskombination, Landwirtschaft, PAK, Schlamm, 2, 3, 7, 8-Tetrachlordibenzo-p-Dioxin, Phthalsäureester, Wassergüte, Ackerhohlform, Dioxine, Kläranlage, Kohlenwasserstoff, Mensch, Nonylphenol, Schwermetall, Pflanze, Tier, Laborversuch
Development and testing of a process to utilize and thermally use recyclings and waste from the purification of exhaust waste and waste water treatment by injecting it into metallurgical melt reactors (1)
No negative effects on blast furnace operations were detected when injecting dried slurry. It was also possible to route the loaded activated coke via the tuyères to the blast furnace process using an intensity of up to 0.8 t/h. While the slurry is being injected, the metallurgical molten result, with the exception of the phosphor content, does not show any significant fluctuations compared to normal operation. The pig iron corresponded with the specified standards (detail information in German).
Development and testing of a process to utilize and thermally use recyclings and waste from the purification of exhaust waste and waste water treatment by injecting it into metallurgical melt reactors (2)
The multi-substance injection plant was technologically and procedurally tested. Up to now several different recyclings such as a mixed plastic granulate difficult to handle from a materials-handling technology point of view were tested. The large-scale testing of the system proved that it is possible to develop and realize reliable dosing and materials handling techniques, especially for large-grain granulates such as slurry, for example (detail information in German).
A reduction of CO emissions to 100 mg/Nm³ with a TOC content of C <1% in the ash was achieved through constructive modifications to a pilot pulsed reactor. The focus of studies carried out to this end were shapes, sizes and positions of aero-valves, as well as the optimisation of the combustion chamber.
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In sewage sludge treatment, the addition of dechlorinating bacteria from suitable sediments leads to separation of chlorineatoms and better availability for further microbial decomposition. Through this, potential pollutant entry into agricultural areas can be prevented in sewage sludge recycling.
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The constituents and long-term behaviour of different waterworks sludges have been investigated using various test processes. It has been demonstrated that, while the intermediate storage of these materials in small-scale, open facilities over a period of several years will not pose any critical hazard, the long-term use of these materials as landfill will require appropriate protective measures.
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