More biogas, less sludge

The disposal of sewage sludge is costly and complex. Breaking down the sludge with ultrasound technology helps yield more biogas, improves sludge dehydration and reduces costs without harming the environment.

Germany has more than 10,000 sewage plants, using costly processes to treat household, industrial and restaurant waste water. The treated water is discharged back into river and lake systems. What remains is an organic / inorganic mixture of sludge. The issue is how to dispose of this residue. Up to now, sewage sludge has been used as an agricultural fertilizer, burned to produce energy or dumped on landfill sites. However, legislation prohibiting the use of landfill sites for the disposal of organic waste is to be introduced in Germany in 2005. The Fraunhofer Institute for Ceramic Technologies and Sintered Materials IKTS, working with the Ingenieurgesellschaft für Wasser und Entsorgung and ultrasound manufacturer Dr. Hielscher have developed a process which can reduce the amount of sewage sludge. Before the sludge completely digests, portions of it are exposed to ultrasound and mechanically broken down. This yields more biogas and makes the sludge easier to dry.
The ultrasound treatment creates microscopic bubbles within the sludge which implode and collapse. With this cavitation, the sludge substances can be broken down, explains Dr. Hannelore Friedrich, head of the IKTS environmental process technology group.The process alters the structure of the sludge particles by releasing and activating enzymes which accelerate and improve the digestion process of the organic material. The resulting gas yield is improved by up to 45 percent. Our new process significantly helps to reduce sewage treatment costs and the investment can be fully amortized within less than four years, Dr. Friedrich continues.Sewage treatment facilities consume less energy and additional materials when dehydrating the sludge. The digestion period is shortened, resulting in more capacity and creating the opportunity to also utilize the digesters to ferment other organic waste. The sewage facilities realize an additional increase in gas yield and a reduction in the amount of sludge that requires disposal.
The process is referred to as split-stream disintegration of sewage sludge using high-performance ultrasound. It has earned its inventors the Joseph-von-Fraunhofer prize and is already being successfully used by eleven sewage treatment facilities in Germany and one in Austria. A license has been sold in Japan. Sewage treatment facilities in England, U.S.A. Canada and Australia have expressed an interest in the process. It is being marketed by IWE.Tec GmbH, a newly formed company based in Radebeul near Dresden.
Joseph-von-Fraunhofer Prize - research with a practical orientation
This prize has been awarded by the Fraunhofer-Gesellschaft every year since 1978, in recognition of outstanding scientific work by members of its staff leading to the solution of application-oriented problems. Over 200 researchers have meanwhile seen their work honored in this way. This year - for the 25th time -, three regular prizes were awarded - each valued at 10,000 euros. An additional prize for special merit is worth 20,000 euros.,For further information,Dr. Hannelore Friedrich ,Telefon [phone] ,[e-mail]
Fraunhofer-Institut fur Keramische Technologien und Sinterwerkstoffe IKTS ,Winterbergstra?e 28 ,D-01277 Dresden ,http://www.ikts.fraunhofer.de/
Link: ,Fraunhofer-Magazin 3.2000 ,http://www.fraunhofer.de/german/publications/df/df2000/mag3-2000_34.html
Klarschlammdesintegration ,http://www.hp-netline.com/umweltreport/Dresden_2001/klaerschlamm.html

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Germany