Homogenization of digestate in a biogas production plant

We supplied 2 vertical agitators for homogenizing liquid effluents for a biogas production plant from urban solid waste in Italy

Biogas is a type of natural gas produced by breaking down the bacteria in municipal organic waste through anaerobic digestion, in biogas production plants. Digestate is the liquid residue of this anaerobic digestion: it must be purified with a wastewater treatment.

Our customer, a company located in the North of Italy, chose the experience of PRO-DO-MIX® for the supply of vertical agitators for the homogenization and denitrification of the digestate. Today we tell you how we faced homogenization, or equalization.


The PRO-DO-MIX® solution: 2 agitators to homogenize the digestate in the Forsu biogas plant

Homogenization is the first phase of digestate purification: this phase takes place in large tanks, where the digestate remains for up to 24 hours, to equalize any daily discharge peaks. The solid concentration of the digestate has an average of about 8%, but the characteristics and densities are variable: homogenization becomes particularly important to make the entire purification process more efficient.

The tank had a volume of 1,000 m3 and a depth of 8.4 m. We therefore designed and supplied 2 GoldenLine agitators, model GPL.A5350.S.800. Due to the high level of liquid in the tank, we equipped the agitators with a high-efficiency 3PM-0030 impeller with a diameter of 3,500 mm.

This impeller ensures exceptional cleaning of the bottom of the tank while pushing the sludge towards the top. Its design optimizes energy consumption, reducing it to only 10 W/m3.


We preferred this solution over the installation of traditional submerged mixers for the following reasons:

Mixing efficiency: Vertical agitators create a flow that allows for a more uniform mixing of the liquid, even in the corners of the tank. This is important to ensure thorough cleaning of the bottom and the even distribution of any chemicals or products.

Ease of maintenance: The control unit (motor and reducer) can be easily removed from the tank for maintenance, facilitating inspection, cleaning, and replacement of parts.

Durability: The control unit of vertical agitators is not immersed in the liquid, making it less susceptible to corrosion and wear. This results in a longer lifespan for the agitator and fewer plant downtimes.


The control group consists of a 15 kW motor and an industrial parallel shaft reducer capable of supporting the impeller thrust, which is 8,000 mm away from the mounting flange. The length of the shaft has also imposed the constructive choice of dividing the shaft into 2 parts, to facilitate transport, installation, and maintenance operations.

These plants are in constant operation, 24 hours a day, 7 days a week: that’s why it’s important to rely on specialists who can design and size the plant as to combine efficiency, sustainability, and reliability.

Are you looking for a customized solution for industrial wastewater treatment 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.

Share On
Share On


Giranti con alto profilo idrodinamico

Il gradiente di velocità interno della girante Evolution è costante dal centro fino all’esterno della pala.
Questo tipo di girante permette l’installazione di una girante con un grande diametro molto vicino al fondo del serbatoio.

Questo rende Evolution perfetta per applicazioni che richiedano un funzionamento in continuo dell’agitatore, anche durante lo svuotamento del serbatoio.


Diametri disponibili da 1650 a 3500 mm

Disponibile una versione smontabile in 3 parti


Other references