The original cost function (A1) for bed filtration is the following:
This function has as variable (x) the filtration flow in millions of gallons per day (mgd). To convert it to Flow (in L / s) the following relationship was used:
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 the same way as explained in the article Cost functions — General.
Based on the above, the following is the function obtained:
