The Sludge Treatment for S&P Wastewater Treatment Plants
The excess sludge production from the rotating immersion disk technology is less than all other biological treatment processes. The developing excess sludge, which is already slightly thickened in the clarification step, has to be stabilized so it can be used further.
The most common stabilization technology is anaerobe digestion. Stabilization happens in every sludge storage tank without any additional technical steps. The sludge storage time is about 180 days in the central European climate. At higher temperatures the sludge storage time can be reduced due to higher biological activity.
However, the possibility to shorten the stabilization time is through the use of aerobe digestion. Via aerators, oxygen air is brought into the excess sludge. This process requires only a fraction of the digestion time of the anaerobe process.
After this, the stabilized sludge can be laid out on land without any further treatment steps. In places where this is not possible, the sludge is conditioned via chemicals for flocculation and precipitation and then dewatered with sludge presses or centrifuges. At the moment, technologies for solar sludge drying are being tested.
The dewatered sludge is burned for thermal energy use.
A natural use of the sludge treatment is to use the sludge on plant beds. The plant roots remove the nutrients of the sludge leaving a residue of pure humus layer. The creation of humus out of excess sludge is also possible via adequate composting technologies. The benefits of such technologies are that the sludge does not contain heavy metals or toxic constituents; otherwise the use of the substrate for gardening and landscaping would not be possible.
System S&P® uses anaerobe digestion if possible. For the rotating immersion disk technology a reduction of the dry matter of the organic load of about 50% can be assumed. This makes the System S&P® rotating immersion disk technology one of the best with the lowest excess sludge quantity.