Sludge treatment
The primary sludge, which accrues during primary clarification, is forwarded via a pumping station to the raw sludge reservoir. The biological surplus sludge, which accrues in the secondary clarification tanks, is condensed via two thickening centrifuges and then also pumped into the raw sludge reservoir.
Here, both forms of sludge are mixed and then forwarded from the reservoir to the digestion towers.
In the digestion towers, the raw sludge is decomposed at around 55°C by micro-organisms and thereby reduced by one third. The energy-rich digester gas (methane content approx. 60-63 per cent) produced during the digestion process is used in the treatment plant’s power station to produce electricity and heating.
During the vegetation period, i.e. the time in which the plants actively grow and develop, the digested sludge is mixed with the irrigation water and utilised as a plant nutrient in the irrigation areas of the Waste water association.
In the winter months, the sewage sludge is not used for irrigation. Instead, the digested sludge is first fed into the digested sludge reservoir, where it is dehydrated using a dehydration centrifuge and the addition of flocking agents. This dehydrated sludge is transported via truck to the sludge storage hall, from where it is used primarily following the cereal harvest in August/September as fertiliser on agricultural areas outside of the Association’s area.
