Reducing digestate viscosity to optimize the dehydration process in centrifuges

In March 2021, BioBANG^® mobile unit has been implied in a test by a Belgian anaerobic digestion plant, treating different types of industrial organic waste (sludge from wastewater treatment, biodiesel by-products, slaughterhouse waste, waste from the potato processing industry, etc.).

An increase in the viscosity of the product, caused by a change in the daily diet loaded into the digesters, led to several problems during the dewatering process carried out by the centrifuges and in the handling of the product with a consequent increase in pump consumption.
The plant operators were looking for a solution to reduce the viscosity of the digestate by optimising dehydration and reducing the consumption of the pumping systems: for this reason, the potential customer turned to BioBANG^® technology. .

Various tests were carried out by taking samples from different points in the plant: “D1, D2, D3 and D4” are samples of digestate taken from four different digesters, while “VTA” is a sample taken on the feeding line between the feeding tank and the digesters.
Laboratory analyses carried out on the untreated (NT) and treated samples for 1 and 3 minutes (1’ e 3’) showed that, due to controlled cavitation, the product viscosity is reduced by 30%.

A reduction in product viscosity allows the sludge dehydration process to be made more efficient and a considerable reduction in the workload of the pumping systems and therefore in their consumption. It will also be possible to reduce the use of water for dilutions and therefore the volumes to be treated.

Thanks to the shock waves released by the imploding cavitation bubbles, the organic molecules are disintegrated, and the chemical bonds broken within the sludge, leading to a greater liquid/solid separation, optimizing the dehydration of the sludge with the centrifuges and making a greater quantity of nutrients (such as organic N and PO2) available within the fertiliser that will be obtained at the end of the process.