Sewage Sludge

Reduction of running costs for sludge treatment and disposal by using disintegration of sludge

The ultrasonic disintegration process developed has proved its value for the reduction of sewage sludge. At the same time, this process has resulted in significantly improved discharge values for sewage treatment plants. Depending upon marginal business management conditions, this process can also contribute to the reduction of operating costs.

Summary

Running costs at sewage plants strongly depend on costs for sludge treatment and disposal. For this reason it is very important to reduce the amount of sludge by accelerating aerobic and anaerobic stabilisation processes.

Use of disintegration technologies with a high specific energy input to destroy bacterial cells or – for the same reason – use of chemical substances as well as thermal effects are common procedures. These methods are either uneconomically in use or not recommended for environmental reasons (e.g. use of tensides).

The main content of this project is to transfer the “low energy disintegration effects” we have received for an improved digestion process into the field of intensified aerobic degradation. Ultrasonic disintegration technology should get introduced at WWTW Roßwein. A split-stream of the whole returned sludge volume is disintegrated by low energy input and together with untreated returned sludge lead into the activated sludge tank. Metabolism activity of micro organisms as well as denitrification rate are increased.

Results:

In connection with the specific surplus quantity the sludge amount for disposal at WWTW Roßwein is reduced by 35 per cent. Moreover it was found a better purification capacity while wastewater treatment and elimination of COD and phosphorus; both of them are very important for environmental reasons.
Potential benefits of the new technology strongly depend on investment and running costs for the whole equipment as well as from costs for sludge disposal. Last-mentioned are very low in case of WWTW Roßwein (30,50 EUR/m³), and only because of that it is not possible to run the technology in Roßwein with profit. This turns into completely profitable not only for environment, but also for economics, if disposal costs increase to a value, which is normal at other sewage plants.
With consideration of the specific circumstances at each sewage plant the results of this project are possible to use at other wastewater treatment plants with simultaneous aerobic degradation.

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Source: German National Library of Science and Technology Hannover (TIB)