The advantageous solution: Anaerobic sludge digestion
Anaerobic sludge stabilisation constitutes the best solution for sewage plants with medium to large design capacity (from approx. 20,000 PE) with regard to cost and energy efficiency and environmental protection.
The anaerobic sludge digestion process
The selected temperature range and the resultant retention time of the sludge in the digester are the most important intake parameters for the design of anaerobic stabilisation. Classic stabilisation takes place in digesters, which represent a type of bioreactor. In roughly 20 days, the sludge is subjected to controlled digestion in an air-free atmosphere and the organic content is converted into water and biogas. The digester gas (biogas) thus released, which consists of a mixture of 50-70% methane, 30-40% CO2, 0-1% steam and trace elements, is combustible and can be used for energy generation purposes.
WABAG has comprehensive experience in the sludge stabilisation field, which derives from a long list of plants of various sizes. The combination of biological wastewater treatment with downstream sludge stabilisation has established itself in many countries as a state-of-the-art concept.
The Teheran South wastewater plant, which is designed for 2.1 million p.e., generates over 80% of its entire electricity and heat requirements in-house. This environment-friendly and economic solution is possible due to an intelligent plant design, which secures the highly efficient use of the biogas derived from the bioreactors.
In this classic process, stabilisation is completed following the digestion process. WABAG has created the new BIOZONE-AD® process on this basis, which raises the volume of biogas generated by up to 40%.