Cost Function for ferric sulfate dosage:

The original cost function (A1) for the ferric sulfate dosage is as follows:

This variable (x) is the dosage capacity of ferric sulfate in lb / h (Pounds per hour). To convert it into a function of the flow rate, the following relationship was used:

Like the other coagulant dosage equations, the dosage of ferric sulfate depends on the quality of the water. Three functions are then proposed, for three levels of raw water quality:

High quality

For this water quality, a usual dose of 1.1 mg / L is taken. With this data, the following replacement of the variables of the equation is proposed:

Additional modifications to this function correspond to the correction of costs per year, with the CCI ENR index of 9547 of the year 2013, to obtain A3. Then part B2 related to the elasticity index is added. This is done in a similar way to that explained in the Cost Functions Wiki — General. In this case, the reference quality of factor B2 changes, in this case corresponding to the maximum limits of good quality, being 4.4 mg / L for sediments and 10 mg / L for nitrogen.

With these data, the function obtained is the following:

Normal quality

For this water quality, a usual dose of 14 mg / L is taken. With this, the following replacement of the variables of the equation is proposed:

Additional modifications to this function correspond to the correction of costs per year, with the CCI ENR index of 9547 of the year 2013, to obtain A3. Then part B2 related to the elasticity index is added. This is done in a similar way to that explained in the Cost Functions Wiki —General. In this case, the reference quality of factor B2 changes, in this case corresponding to the maximum limits of regular quality, being 56 mg / L for sediments and 20 mg / L for nitrogen.

With these data, the following is the obtained function:

Low to very Low quality

For this water quality, a usual dose of 50.8 mg / L is taken. With this data, the following replacement of the variables of the equation is proposed:

Additional modifications to this function correspond to the correction of costs per year, with the CCI ENR index of 9547 of the year 2013, to obtain A3. Then part B2 related to the elasticity index is added. This is done in a similar way to that explained in the Cost Functions Wiki — General. In this case, the reference quality of factor B2 changes, in this case corresponding to the maximum limits of regular quality, being 200 mg / L for sediments and 30 mg / L for nitrogen.

Therefore, the function obtained is the following:

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