Sewage Sludge
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).
Using the technology mentioned above the purification efficiency concerning organic waste load and nitrogen does in no way lack behind that of modern large-sized sewage treatment plants. Investment and running cost as well as technological expenditures are comparable with sewage plants without advanced treatment.
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Cleaning of tannery waste water by means of 1. partial current biology chromium-containing waste water, 2. main biology chromium-free, alkaline waste water
In addition to the chromium recuperation a leather factory uses a biological partial current treatment to remove chromium from the waste water of the enterprise. The separated and to a large extent chromium-free sludges can be reused. The chromium emissions could be clearly decreased and the COD content lowered by more than 90 %. By the applied procedure a third of the entire operating costs (waste water treatment, disposal) were saved.
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The process concept developed represents a practicable alternative to centralised manure treatment on an industrial scale. Within a short space of time and with only limited investment, a demonstrable reduction in the contamination of agricultural land with nutrients can be achieved.
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Ultrasonic treatment is a proven method for the stabilisation of activated sludges. The process developed, which has been tested in the laboratory and in pilot installations, is mobile and can be applied in sewage treatment plants on a seasonal and short-term basis.
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A growing population and increasing tourism on Sal island meet inadequate drinking water supply and wastewater disposal concepts. Against this background, Prack Consult GmbH installed a container sewage treatment plant with integrated sewage sludge treatment for a pilot test. It showed good purification efficiency under local arid conditions.
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Keywords:
Abwasserentsorgung, Klärschlammbehandlung, Schilf, Kläranlage
Development of a process to influence nutrient content in the further treatment of stabilised sewage sludge
Using an aerobic-anoxic secondary treatment process, it has been possible to reduce the proportion of nitrogen in sewage sludge and in process water from waste water treatment by 60% and 85% respectively. At the same time, it has been possible to reduce the dry weight of sewage sludge by up to 50%.
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Dimensioning and operating parameters for the activated sludge process as a function of temperature and salinity
The project partners examine the effects of temperature and salinity on reduction rates and minimum sludge age in activation basins. The results can be used to design sewage plants for non-moderate climate zones for which no experimental but only calculated base data so far exists.
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Keywords:
Belebungsverfahren, Belebtschlamm, Temperaturabhängigkeit, Anlagenbemessung
Elimination of nutrients in sewage treatment plants through multi-stage process control and the use of surplus sludge in external reaction spaces
In conjunction with the extension of a sewage treatment plant, a multi-stage process based upon biological phosphate removal and (de)nitrification has been implemented on an industrial scale. This has resulted in clear cost savings in relation to optimised standard solutions, associated with an improved energy balance and the smaller structural dimensions of the installation.
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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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Half-technical investigations regarding thermic sewage sludge desintegration for an increase of the biogas yield and a reduction of the sludge volume
An initial unit for thermal disintegration of sewage sludge has been integrated in an operational municipal sewage treatment plant. As a result, there has been a significant reduction of the quantity of sludge requiring disposal. Cost-effective operation of a unit for thermal disintegration is possible in sewage treatment plants serving communities with at least 80,000 inhabitants.
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