Denitrification of digestate in biogas production from urban solid waste

Agitator for denitrification in a 1400 m3 tank with a concentration of 30 g/l of suspended solids

We designed and supplied 6 vertical agitators for the denitrification of liquid effluents in a biogas production plant from municipal solid waste  in Italy

Biogas production plants from the organic fraction of urban solid waste produce biogas through an anaerobic digestion process. Digestate, the liquid residue of the anaerobic digestion of waste, must be treated and purified – through various phases – before being reintroduced into the water network.

Today we tell you how PRO-DO-MIX® designed and supplied the vertical agitators for the denitrification of the digestate in the biogas plant of an Italian customer. For the same project, we also supplied the agitators for the homogenization of the digestate.


The PRO-DO-MIX® solution: 6 agitators to denitrify the digestate in a Forsu biogas plant

Denitrification is the phase following the homogenization of the digestate. During this process, which takes place in the absence of oxygen, the nitrogen compounds present in the digestate in the form of NO3 are transformed into inert nitrogen N2, thanks to the “work” of facultative heterotrophic bacteria.

In this case, we had 3 denitrification tanks, each with a volume of 950 m3, a constant liquid level of 6 m and a maximum concentration of suspended solids of 30 g/l. For our client, we designed and supplied 6 vertical agitators of the BEL.A1262.Q.500 model, two per tank, with a high-efficiency 3PM-0030 impeller with a diameter of 2600 mm: the design ensures highly efficient mixing and energy consumption of only 6 W/m3.

Denitrification of digestate is a delicate phase: bacteria must enjoy optimal environmental conditions to perform their task to the best of their ability. For this reason, it is necessary to correctly size the agitators and impellers, relying on partners who, like PRO-DO-MIX®, have decades of experience in the sector. 

Another fundamental requirement for agitators is reliability: denitrification tanks are in operation 24 hours a day, 365 days a year, without interruption, and a failure of the agitators would result in economic damage to the customer, as well as a safety problem.

If you are looking for a customized and reliable solution for the treatment and purification of industrial wastewater in the biogas production sector, you can count on the experience and success stories of PRO-DO-MIX®.


Contact us now for the supply of vertical agitators and customized solutions.

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Impellers with high hydrodynamic profile

Three-blade impeller with high hydrodynamic profile. It is the “evolution” of Hurricane. Its internal velocity gradient, constant from the centre to the edge of the blade, allows the positioning of an impeller with large diameter very close to the bottom of the tank. That makes Evolution perfect for applications that require the mixer’s continuous operation during the total draw-off of the tank.

It can be manufactured with different diameters, 1650 to 3500 mm.

A completely disassemblable option is available as well, to ease the entering through the tank manhole.


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