Cost function for filter back-washing water-air:

The original cost function (A1) for air-water washing is as follows:

This has as a variable (x) the total area of the facility in ft2 (square feet). To convert it to the variables available to the system (flow rate), the following relationship was used to express that area as a function of flow rate:

Where C represents the hydraulic load, with a 350 m/d value of in terms of flow:

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.

According to the above, the following is the function obtained:


Bibliography

Preliminary Cost Estimation Models for Construction, Operation, and Maintenance of Water Treatment Plants. 2013. Jwala R. Sharma, Ph.D., M.ASCE; Mohammad Najafi, Ph.D., P.E., F.ASCE; and Syed R. Qasim, Ph.D., P.E., M.ASCE. | https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29IS.1943-555X.0000155

Referencies

Asistencia de aire en el lavado a contracorriente | https://www.gardnerdenver.com/en-my/hoffmanandlamson/industries/water-and-wastewater-treatment/filter-backwash