According to the present invention, there is provided a treatment process system for biomass material and methods for such system. The system comprises a first dewatering stage arranged to receive biomass material, to remove liquid from the biomass material, and to feed the biomass material forward in the process. Further, the system includes a water treatment stage arranged to collect the removed liquid and an addition stage located downstream said dewatering stage and operatively coupled to the first dewatering stage. The addition stage is arranged to receive the de-watered biomass material, wherein the addition stage includes inlets for adding acid containing solution into the addition stage. A reactor stage arranged to receive the biomass material treated in the addition stage and to perform a pre-hydrolysis process to the biomass material. A filtrate feeding arrangement is arranged to feed liquid from the filtrate tank to the reactor stage.