Editing Microfiltration (section)

===Design economics===

The cost to design and manufacture a membrane per unit of area are about 20% less compared to the early 1990s and in a general sense are constantly declining.<ref>Mullenberg 2009, 'Microfiltration: How Does it compare, Water and wastes digest, web log post, December 28, 2000, accessed 3 October 2013,<http://www.wwdmag.com/desalination/microfiltration-how-does-it-compare.></ref>  Microfiltration membranes are more advantageous in comparison to conventional systems. Microfiltration systems do not require expensive extraneous equipment such as flocculates, addition of chemicals, flash mixers, settling and filter basins.<ref>Layson A, 2003, Microfiltration – Current Know-how and Future Directions, IMSTEC, accessed 1 October 2013 {{cite web |url=http://www.ceic.unsw.edu.au/centers/membrane/imstec03/content/papers/MFUF/imstec152.pdf |title=Archived copy |access-date=2013-10-15 |url-status=dead |archive-url=https://web.archive.org/web/20131015111520/http://www.ceic.unsw.edu.au/centers/membrane/imstec03/content/papers/MFUF/imstec152.pdf |archive-date=2013-10-15 }}> University of New South Wales. p6</ref>  However the cost of replacement of capital equipment costs (membrane cartridge filters etc.) might still be relatively high as the equipment may be manufactured specific to the application. Using the design heuristics and general plant design principles (mentioned above), the membrane life-span can be increased to reduce these costs.

Through the design of more intelligent process control systems and efficient plant designs some general tips to reduce [[operating costs]] are listed below<ref>Layson A, 2003, Microfiltration – Current Know-how and Future Directions, IMSTEC, accessed 1 October 2013 <{{cite web |url=http://www.ceic.unsw.edu.au/centers/membrane/imstec03/content/papers/MFUF/imstec152.pdf |title=Archived copy |access-date=2013-10-15 |url-status=dead |archive-url=https://web.archive.org/web/20131015111520/http://www.ceic.unsw.edu.au/centers/membrane/imstec03/content/papers/MFUF/imstec152.pdf |archive-date=2013-10-15 }}> University of New South Wales. p6</ref>

* Running plants at reduced fluxes or pressures at low load periods (winter)
* Taking plant systems off-line for short periods when the feed conditions are extreme.
* A short shutdown period (approximately 1 hour) during the first flush of a river after rainfall (in water treatment applications) to reduce cleaning costs in the initial period.
* The use of more cost effective cleaning chemicals where suitable (sulphuric acid instead of citric/ phosphoric acids.)
* The use of a flexible control design system. Operators are able to manipulate variables and setpoints to achieve maximum cost savings.

Table 1 (below) expresses an indicative guide of membrane filtration capital and operating costs per unit of flow.

{| class="wikitable"
|-
! Parameter !! Amount !! Amount !! Amount !! Amount !! Amount
|-
| Design Flow (mg/d)|| 0.01|| 0.1 || 1.0|| 10 || 100
|-
| Average Flow (mg/d) || 0.005 || 0.03 || 0.35|| 4.4 || 50
|-
| Capital Cost ($/gal) || $18.00 || $4.30 || $1.60 || $1.10 || $0.85
|-
| Annual Operating and Managing Costs ($/kgal) || $4.25 || $1.10 || $0.60 || $0.30 || $0.25
|}

Table 1 Approximate Costing of Membrane Filtration per unit of flow<ref>Microfiltration/Ultrafiltration, 2009, Water Research Foundation, accessed 26 September 2013; <{{cite web |url=http://www.simultaneouscompliancetool.org/SCToolSmall/jsp/modules/welcome/documents/TECH7.pdf |title=Archived copy |access-date=2013-10-15 |url-status=dead |archive-url=https://web.archive.org/web/20140309015714/http://www.simultaneouscompliancetool.org/SCToolSmall/jsp/modules/welcome/documents/TECH7.pdf |archive-date=2014-03-09 }}></ref>

Note:

* ''Capital Costs are based on dollars per gallon of the treatment plant capacity''
* Design flow is measured in millions of gallons per day.
* Membrane Costs only (No Pre-Treatment or Post-Treatment equipment considered in this table)
* Operating and Annual costs, are based on dollars per thousand gallons treated.
* All prices are in US dollars current of 2009, and is not adjusted for inflation.''