4274Design

The sludge screw press and finances

The sludge screw press and finances

On the extensive land of the clearing plant of the waste water association upper lauer north of poppenlauer stands for some months a third hall. It protects a so-called screw press, which was newly purchased and dewaters the clarified sludge from the clarification plants of poppenlauer and recently also from munnerstadt.

For a few days now, the plant has been producing a black substance that laymen could mistake for coal from the coal cellar. It is not combustible, however, because it still contains 70 percent water, and it is not odorless like coal. All in all, the new plant cost a good half million euros, which the member municipalities have to pay as a levy.

Dewatering more and more expensive

The clarification plant in poppenlauer produces about 8000 cubic meters of clarified sludge per year with a water content of about 97.5 percent. In the past, it was used as a fertilizer in agriculture, but this is hardly possible today due to strict regulations. Every few months, an external service provider used to come and dewater this clear sludge with his mobile press. The dewatered substance was then taken to a cement plant in karlstadt – not as fuel, however, but as a coolant for the incineration process. "Dewatering has become more expensive from year to year", mabbach mayor matthias klement (CSU), who is also chairman of the upper lauer wastewater association, explained at a local meeting.

Similar problems had the city of munnerstadt. The clearing plant produces about 3500 cubic meters of clear sludge per year, which also has to be pressed and then disposed of. Munnerstadt is anyway a member of the wastewater association upper lauer, because the eastern parts of the city are connected to its clearing plant. The wastewater from the two western districts of burghausen and reichenbach, however, is clarified in the clarification plant of the saale-lauer wastewater association in hohenroth.

How the screw press works?

In total about 11.500 cubic meters of clear sludge (including munnerstadt) per year are now freed from part of their water content in the new screw press. It is not possible to see from the outside how it works. On the website of the manufacturer leiblein gmbh hardheim it says (somewhat abbreviated) "basically, the screw press consists of an internal screw shaft with a jacketed screen drum or a screw conveyor. A seven-cylinder. The flocculated sludge is pumped into the screening drum. The screw rotates and forces the sludge towards the sludge discharge, where there is a resistance (back pressure cone) against which the sludge is pressed. The filtrate is printed through the surrounding screen jacket. The filtrate runs off via a filtrate drain. The further the sludge is transported to the back, i.E. In the direction of the resistance, the coarser the volume reduction and the higher the pressure on the sludge. This squeezes even more liquid out of the sludge, which runs off as filtrate. Finally, the dewatered sludge leaves the screw press via the sludge discharge".

Running unattended

The plant is fully electronically controlled and can run unattended around the clock, especially since it shuts down automatically in the event of a defect. What remains is the already mentioned black mass. When enough has accumulated again, it will be transported away. Where to? This is to be put out to tender again in the near future. In total, the new plant has 506.000 euro, of which construction engineering 189.000 euros, the hall 65.000 euros, electrical installations 27.000 euros, ruhrwerke 11.000 euros and finally the actual screw press 214.000 euro.

The sludge dewatering plant is financed by an investment levy paid by all member municipalities. It is based on the number of primary residents connected to the clearing system at the end of the last five years. The largest contributor is mabbach with 32.91 percent, followed by stadtlauringen with 30.29 percent, munnerstadt with 15.74 percent, thundorf in unterfranken with 7.82 percent, uchtelhausen with 11.67 percent and sulzfeld with 1.57 percent.

Must munnerstadt pay more?

Even now clear mud from munnerstadt is already being pressed in poppenlauer. The contract between the wastewater association and the city of munnerstadt for the delivery of clear sludge, which was supposed to be approved at the most recent meeting of the association’s assembly, has not yet been finalized. The deputy chairman and mayor of the town of lauringen friedel heckenlauer had thrown into the discussion that munnerstadt should now be considered with more population equivalents (pollution load per inhabitant) than before and thus also be asked to pay more. That is why they are now renegotiating.

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