Reduction of excess sludge by up to 80% with ozone injection – Practical Experience

Wolff, S.1, Hurren, D.2
1Air Liquide Technology Centre, Germany, 2Air Liquide UK


Since 2001, AIR LIQUIDE has been operating several industrial ASPAL-Sludge-plants in Germany and Europe which reduce
the amount of excess sludge considerably.

The patented ASPAL-Sludge-process is effected by injecting ozone into the activated sludge in the bypass which leads to the
biological step of the waste water treatment process. The two main advantages are: 1) disintegration of secondary excess
sludge 2) decrease of filamentous bacteria. A reduction by 40 – 80 % of the secondary sludge excess is attainable.
Actual sludge reduction rates and influences on process parameters are reported with from a number of treatment works...
For this purpose, current operated plants of different industrial sectors have been chosen. Finally, an overview of the operating
expenses of the ASPAL-Sludge-application is given.

Excess sludge, surplus sludge, waste sludge, reduction, filaments, disintegration, ozone, waste water treatment

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