sludge digestion unit, wastewater treatment plant Alexandria East (Egypt)

Before the construction of the digestion unit, the sludge produced by the East Alexandria wastewater treatment plant was subject to a dewatering process, followed by transportation via trucks to a landfill located 45km away. The new digestion unit makes the Alexandria Wastewater Treatment Plant more sustainable transforming sewage sludge into green energy to meet the environmental, social and economic challenges of the city of Alexandria. One of main challenges was to integrate strong health, safety and environmental constraints due the expansion of the town close to the plant.

Key figures

• 4 digesters of 16 000 m³ each,
• up to 35% reduction of the sludge volume,
• up to70% electricity self-sufficiency,
• up to 65% Greenhouse Gas emissions reduction compared to the existing plant, taking into account the construction and the operation.

Sludge digestion and energy production

The digestion Digelis®, based on mesophilic anaerobic digestion produces biogas that is converted into electricity and heat (cogeneration) for the wastewater plant's energy needs. The plant includes 4 XL-sized digesters to achieve a high level of energy self-sufficiency.
An advanced sludge mixing [Geyser pump] is required to ensure optimum biogas production and sludge mineralization / stabilization for this type of large digesters.