Separation - Dewatering of Digester Solids

Separation or dewatering of digester solids has become a common process amongst bio-digesters in order to obtain an easier storable product and manage nutrients a the same time.

Depending on the substrate and the separation technology applied 10 - 35% of total nitrogen (N) and 10 - 90% of total phosphorous (P) can be removed from the liquid phase.

Besides the nutient management separation has some handling advantages for the liquid phase:

• No build up of floating layers or crusts and no bottom sludges.

• Homogenization i.e. mixing befor spreading is not necessary.

• Hauling and spreading requires a simpler technology.

• Liquids can go back to the process to adjust dry matter content.

• Solids are easily storable, stabilised and can be used as soild conditioner or bedding.

To dewater digester solids the following technilogies can be applied:

• Screw Press Separator

• Centrifuge, Decanter