A separation system for the separation and purification of biomolecules, said separation system comprising: first (1;21), second (3;22) and third (5;23) separation units, selected from columns and filters, and wherein at least two thereof are chromatography columns, each separation unit comprising a fluid inlet and a fluid outlet, wherein the fluid outlet of the first separation unit and the fluid inlet of the second separation unit are connected by a first main conduit (2;24) and the fluid outlet of the second separation unit and the fluid inlet of the third separation unit are connected by a second main conduit (4;25), wherein the first separation unit provides an outflow liquid to the first main conduit and the second separation unit provides an outflow liquid to the second main conduit; fluid-delivery devices (41,53) fluidly coupled to the first and second main conduits through branch conduits (8,9;42,54) that joins the first and second main conduits at junctions (43,55) between the first and second separation units and second and third separation units respectively; and in-line sensors (45,57) operably coupled to the first and second main conduits between each junction and the inlets of the second and third separation units respectively, the in-line sensors configured to monitor an environmental property parameter of a streams of liquid flowing through the first and second main conduits between the first and second separation units and second and third separation units respectively, the fluid-delivery devices configured to, via a closed loops each comprising the in-line sensor and a controller (46,58), provide incoming liquids into the first and second main conduits as the streams of liquid flows there through to adjust the environmental property parameter, the incoming liquids combining with the outflow liquids at the junctions. first (1;21), second (3;22) and third (5;23) separation units, selected from columns and filters, and wherein at least two thereof are chromatography columns, each separation unit comprising a fluid inlet and a fluid outlet, wherein the fluid outlet of the first separation unit and the fluid inlet of the second separation unit are connected by a first main conduit (2;24) and the fluid outlet of the second separation unit and the fluid inlet of the third separation unit are connected by a second main conduit (4;25), wherein the first separation unit provides an outflow liquid to the first main conduit and the second separation unit provides an outflow liquid to the second main conduit; fluid-delivery devices (41,53) fluidly coupled to the first and second main conduits through branch conduits (8,9;42,54) that joins the first and second main conduits at junctions (43,55) between the first and second separation units and second and third separation units respectively; and in-line sensors (45,57) operably coupled to the first and second main conduits between each junction and the inlets of the second and third separation units respectively, the in-line sensors configured to monitor an environmental property parameter of a streams of liquid flowing through the first and second main conduits between the first and second separation units and second and third separation units respectively, the fluid-delivery devices configured to, via a closed loops each comprising the in-line sensor and a controller (46,58), provide incoming liquids into the first and second main conduits as the streams of liquid flows there through to adjust the environmental property parameter, the incoming liquids combining with the outflow liquids at the junctions.