A system (1) for the treatment of a fluid comprising at least two of the fractions solid particles, liquid and/or gas is described, the system (1) being defined by at least one inlet portion (3) and two or more outlet portions (5, 7, 9), and the system (1) being arranged to separate solid particles over a predetermined size from the liquid by means of at least one screening apparatus (23, 25) andthen carry said fractions out of the system (1), the system (1) for the treatment of fluid being substantially fluid-tight between said at' least one inlet portion (3) and the outlet portions (5, 7, 9) and being provided with at least one underpressure-generating device (11, 13) which is arranged to provide an underpressure in the system (1) between said at least one inlet portion (3) and the outlet portions (5, 7, 9), the at least one screening apparatus (23, 25) being arranged to separate the fluid into fractions substantially including solids, liquid and/or gas, the fractions of the fluid being kept separate as the fractions are carried out of the system (1). Also described is a method of using the system (1).