A method for controlled mixing of a plurality of substances to produce a first mixture, the method comprising: receiving a first target concentration range of a first substance in the mixture of the plurality of substances; supplying the plurality of substances to a first mixing zone (112, 512), the plurality of substances mixing in the first mixing zone to produce the first mixture; determining a concentration value of the first substance in the first mixture while continuing to supply the plurality of substances to the first mixing zone (112, 512); comparing the concentration value of the first substance to the first target concentration range; and upon determining that the concentration value of the first substance falls outside the first target concentration range, automatically adjusting a flow rate of the first substance to the first mixing zone (112, 114, 512) by adjusting an opening size of a control valve provided at a first conduit (110, 510) for supplying the first substance to the first mixing zone (112, 114, 512), the opening size of the control valve adjusted based on the concentration value of the first substance in the first mixture and based on one or more physical characteristics of at least one of the plurality of substances, wherein the one or more physical characteristics are selected from a group comprising viscosity, density, specific gravity, chemical composition, temperature and pressure characterised in that the method comprises adjusting the control valve by: determining a difference value between the concentration value of the first substance and the first target concentration range; creating an adjusted control parameter after determining that the post-mixing concentration is outside the first target concentration range, determining a feedback control value based on the difference value and the adjusted control parameter; and adjusting the control valve based on the feedback control value. receiving a first target concentration range of a first substance in the mixture of the plurality of substances; supplying the plurality of substances to a first mixing zone (112, 512), the plurality of substances mixing in the first mixing zone to produce the first mixture; determining a concentration value of the first substance in the first mixture while continuing to supply the plurality of substances to the first mixing zone (112, 512); comparing the concentration value of the first substance to the first target concentration range; and upon determining that the concentration value of the first substance falls outside the first target concentration range, automatically adjusting a flow rate of the first substance to the first mixing zone (112, 114, 512) by adjusting an opening size of a control valve provided at a first conduit (110, 510) for supplying the first substance to the first mixing zone (112, 114, 512), the opening size of the control valve adjusted based on the concentration value of the first substance in the first mixture and based on one or more physical characteristics of at least one of the plurality of substances, wherein the one or more physical characteristics are selected from a group comprising viscosity, density, specific gravity, chemical composition, temperature and pressure characterised in that the method comprises adjusting the control valve by: determining a difference value between the concentration value of the first substance and the first target concentration range; creating an adjusted control parameter after determining that the post-mixing concentration is outside the first target concentration range, determining a feedback control value based on the difference value and the adjusted control parameter; and adjusting the control valve based on the feedback control value. determining a difference value between the concentration value of the first substance and the first target concentration range; creating an adjusted control parameter after determining that the post-mixing concentration is outside the first target concentration range, determining a feedback control value based on the difference value and the adjusted control parameter; and adjusting the control valve based on the feedback control value.