Simulated cost comparisons of hollow-fiber and integrated nanofiltration configurations

Treatment costs and cost effectiveness of a hollow-fiber nanofiltration (HF NF) system vs. an integrated system comprised of, spiral-wound nanofiltrati on (SWNF) pre-treated with hollow-fiber ultrafiltration (HFUF) are estimate d and compared using numerical simulation and cost modeling. Optimal select ions are investigated based on the cost effectiveness of the two treatment options over different raw water conditions and for different plant capacit ies. Recently developed permeate flux and cost models were used to simulate the membrane systems. Values for operating parameters used in the simulati ons were chosen from previously reported pilot studies. For relatively smal ler (less than or equal to 1 mgd) plants, a NFNF system that can handle hig her solids loading is predicted be the cost effective treatment option, due to the associated lower non-membrane capital costs that form the dominant component of total treatment costs at smaller capacities. However, when the raw water is largely characterized by particles with a very high Fouling p otential for the single HFNF step, separate HFUF pre-treatment for particul ate removal may be warranted. Al higher plant capacities, economies of scal e are shown to be significantly realized in non-membrane capital costs, and the integrated HFUF-SWNF configuration is predicted to become increasingly cost effective due to the cost advantages of spiral-wound membranes. Hence , optimal design philosophies with regard to cost effectiveness may be quit e different for small and large membrane plants. (C) 2000 Elsevier Science Ltd. All rights reserved.