Filter device (1, 14, 35, 40, 46, 54) for separating a mixture of solid substance and a liquid, comprising: - a first compartment (2, 15, 55) adapted to hold a mixture of solid substance and a liquid, - a second compartment (6, 16, 57) positioned at least partially under the first compartment (2, 15, 55) for collecting liquid coming from the first compartment (2, 15, 55), - a stationary open support structure (4, 17, 59) which separates the first compartment (2, 15, 55) and the second compartment (6, 16, 57) and which is adapted to support a filter belt (36, 39, 41, 49, 61) displaceable through the first compartment (2, 15, 55), - at least one axially rotatable first transport element (11, 19a, 19b, 38, 43, 47a, 47b, 60a, 60b) which engages on the support structure (4, 17, 59) and which is adapted for pushing displacement of the filter belt (36, 39, 41, 49, 61) from a feed side of the support structure (4, 17, 59) in the direction of a discharge side of the support structure (4, 17, 59) by means of rotating the first transport element (11, 19a, 19b, 38, 43, 47a, 47b, 60a, 60b) and by clamping the filter belt (36, 39, 41, 49, 61) between the first transport element (11, 19a, 19b, 38, 43, 47a, 47b, 60a, 60b) and the support structure (4, 17, 59), - at least one axially rotatable second transport element (12, 23, 39, 44) characterised in that the axially rotatable second transport element (12, 23, 39, 44) engages on the first transport element (11, 19a, 19b, 38, 43, 47a, 47b, 60a, 60b) and co-acts with the first transport element (11, 19a, 19b, 38, 43, 47a, 47b, 60a, 60b), and which is adapted for pulling displacement of the filter belt from the feed side of the support structure (4, 17, 59) in the direction of the discharge side of the support structure (4, 17, 59) by means of rotating the second transport element (12, 23, 39, 44) and by clamping the filter belt between the first transport element (11, 19a, 19b, 38, 43, 47a, 47b, 60a, 60b) and the second transport element (12, 23, 39, 44), and in that at least one drive element (21, 42, 62) coupled to at least one transport element for causing axial rotation of the transport elements. - a first compartment (2, 15, 55) adapted to hold a mixture of solid substance and a liquid, - a second compartment (6, 16, 57) positioned at least partially under the first compartment (2, 15, 55) for collecting liquid coming from the first compartment (2, 15, 55), - a stationary open support structure (4, 17, 59) which separates the first compartment (2, 15, 55) and the second compartment (6, 16, 57) and which is adapted to support a filter belt (36, 39, 41, 49, 61) displaceable through the first compartment (2, 15, 55), - at least one axially rotatable first transport element (11, 19a, 19b, 38, 43, 47a, 47b, 60a, 60b) which engages on the support structure (4, 17, 59) and which is adapted for pushing displacement of the filter belt (36, 39, 41, 49, 61) from a feed side of the support structure (4, 17, 59) in the direction of a discharge side of the support structure (4, 17, 59) by means of rotating the first transport element (11, 19a, 19b, 38, 43, 47a, 47b, 60a, 60b) and by clamping the filter belt (36, 39, 41, 49, 61) between the first transport element (11, 19a, 19b, 38, 43, 47a, 47b, 60a, 60b) and the support structure (4, 17, 59), - at least one axially rotatable second transport element (12, 23, 39, 44)