Berghof tubular UF membranes are used for nutrient valorization as a direct filtration process, with a reverse osmosis post-treatment usually applied for obtaining a concentrated and high-value biofertilizer.

Tubular UF membranes remove the particles, colloids, and macromolecules. The ability of tubular membranes to handle high concentrations of suspended and colloidal matter allows the operation with high recovery, even when dealing with complex and high-loaded digestate. Particulate carbon and nutrients are partially removed in the UF reject stream, which is sent back to the centrifugation for recovery as dry material that can be reused in agriculture. Most of the nutrients are preserved and recovered in the UF permeate: with SDI values lower than 3, it presents the optimum quality to be treated with a final two-pass reverse osmosis system. The RO reject consists of a concentrate liquor containing dissolved nutrients (NPK) to be used as high-value fertilizer, whereas the RO permeate is a high-quality treated water complying with the most stringent requirements for discharge or reuse.