The WABAG ENOPUR® System: A Sustainable Solution for Sludge Treatment and Energy-Neutral WWTPs.

• Conversion of residues into an energy source.
• Producing Green Energy.

The WABAG ENOPUR® system provides a comprehensive approach to sustainable sludge treatment, enabling energy-neutral wastewater treatment plants (WWTPs). The following processes are included:

Sludge Thickening (Pre-Treatment):
Thickening prior to stabilization significantly

• reduces sludge volume,
• decreases hydraulic load on the digester,
• enhances gas yield, and
• increases heat retention.

Anaerobic Sludge Digestion:
The anaerobic digestion process depends on critical design parameters like the selected temperature range and the sludge retention time within the digester.

• • In this process, stabilization occurs in bioreactor-like digesters over approximately 20 days.
  • Under air-free conditions, organic content in the sludge is converted into water and biogas.
  • The resulting biogas, containing 50–70% methane, 30–40% CO2, trace amounts of steam, and other elements, is combustible and serves as an energy source

Producing green energy – putting biogas to work

The calorific value of the gas produced in the digesters during anaerobic stabilization is approximately 6.5 kWh/m3, making it a valuable source of green energy. Efficient utilization allows for largely independent energy supply, covering up to 100% of energy needs for large treatment plants through in-house generation.

If the biogas is employed for energy generation purposes, electrical and thermal energy can be obtained for the in-house supply of treatment plants or feeding into the public grid.   

• Generation of electrical energy and waste heat in a unit heating power
• Direct employment in gas engines
• Thermal utilisation through the generation of steam or hot water.

Post-Treatment Processes:
During post-treatment, the sludge should be dewatered to the greatest possible extent. This results in a further reduction in sludge volume and thus eases the load on downstream process phases. 

Depending on the sludge characteristics and the process used, stabilised sewage sludge demonstrates a dry substance content of 2-4%. All in all, stabilisation results in a roughly 30% reduction in solids. If gravity or mechanical post-thickening is employed, the dry substance concentration increases to 4-7%.

• Dewatering via centrifuges or filter presses raises the dry substance to 20–35%.
• Further drying (e.g., in a fluidized bed) achieves up to 95% dry substance, enabling thermal utilization as supplementary fuel or for agricultural use.

Key Features of the ENOPUR^® system:

• Reduction in organic content by ~50% with conversion into combustible biogas.
• Production of renewable energy.
• Possibility of independent energy supply for treatment plants, leading to energy-neutral WWTPs.
• Reduced operating costs, stable process, and smaller footprint.
• Reduction in the volume of malodorous substances and sludge hygienization.
• Climate protection through an improvement in the CO2 balance of the treatment plant.

WABAG has extensive experience in all technological aspects related to anaerobic sludge treatment plants, including the design of digesters (shape, mixing solutions, and choice of heat exchangers and gas storage) as well as pre- and post-treatment processes and components such as sludge thickening, dewatering, drying, and biogas desulphurization.

Depending on specific plant demands, optimal results can be achieved through dual stabilization, combining aerobic and anaerobic processes.

For more information, please ask for our brochure “ENOPUR® Energy-Optimized Sludge Treatment Systems.” or contact our experts directly.