Cost Modeling and Estimation of Crossflow Membrane Filtration Processes

A model is presented for estimating costs of crossflow ultrafiltration and microfiltration processes. The model incorporates separate correlations for several major components of capital costs, thus accounting for different economies of scale associated with different equipment and facilities. In contrast to previous cost-modeling exercises that have inherently assumed an economy of scale for capital costs based on current design estimates, this work considers an economy of scale for the entire membrane system that changes with the design mix as the capacity of the facility increases. The calibrated model is used to explore the impacts of raw water quality, plant capacity, and operating variables on treatment costs. Capital costs amortized per unit of production decrease with plant capacity due to economies of scale. The overall economies of scale associated with a membrane system are considered as a function of the raw water quality and the resultant permeate flux. When permeate flux is limited due to concentration polarization and cake growth, treatment costs are predicted to demonstrate relatively lower economies of scale. Selection of a combination of design and operating parameters such as membrane radius, transmembrane pressure, and system recovery, which results in higher permeate fluxes for a given raw water quality, is predicted to lower total treatment costs. Key words: Cost model; economics; membrane filtration; membrane process; microfiltration; ultrafiltration; water treatment