[[Image:iron filter icon.png|right]]
[[Image:iron filter.jpg|thumb|right|250px|Building an iron filter. <br>Photo: PCWS]]
==Construction, operations, and maintenance==
'''====IRF'''<br>====
To use it for the first time, the filter is filled with water and allowed to overflow a little. The first discharge is turbid from the gravel, but this clears up after a day or so of use. After placing their buckets under the tap, the users just pump the hand pump, and by gravity the water enters and flows
through the filter, displacing the previous treated contents, which then overflows thru the taps into their buckets.
sedimentation space, a drain can be opened to clean this out. The worst that can happen is that the unit may eventually need overhauling. All parts are then taken out and cleaned, and clogs and leaks repaired.
====Biologically-enhanced method==== '''Surface area requirement''Biologically'<br> A filter of approximately 1 m2 surface area is necessary to deliver filtered water at a rate of about 0.25 l/s (assuming that guidelines on head and filter sand size / depth are followed). '''Sand depth and size'''<br> A sand bed depth of 0.15 m is capable of consistently reducing iron concentrations of about 7 mg/l to <0.3 mg/l. Such consistent performance is achievable with a sand of 1.18 mm effective size. This sand needs a 0.05 m deep gravel support layer to ensure that it does not escape through the hacksaw cut slots in the drainage bar. '''Head requirements and the need for ballast'''<br> The head needed to deliver an acceptable flow rate of 0.2-0.3 l/s in unclogged sand is 50 mm. This will increase as the filter clogs. To raise the water level from the top of the sand to a height of 50 mm requires 50 l of water to be pumped (assuming 1 m2 surface area), and therefore it would take 3 minutes of pumping just to reach the desired flow rate. This delay may be largely overcome by adding ballast to the filter. In our Ugandan trial water-enhanced methodfilled plastic bags were used as ballast. This approach worked well, taking only 29% more time to fill a jerrycan from the filter than it took directly from the handpump. It may be possible to improve this performance but further work is needed to assess the effect of ballast on the iron removal process. '''Aeration'''<br> The water entering the filter must contain some oxygen in order to promote the oxidation of iron. Do some checks on the DO from the handpump itself. The water only needs to reach about 40-50% oxygen saturation and this may be achieved due to the aeration that naturally occurs in the handpump spout plus that provided by a perforated aeration plate.
[[Image:bio iron filter.jpg|thumb|center|600px|Sketch diagram of the iron removal filter. Diagram: Dr Sean Tyrrel, Cranfield University.]]
For greater detail about construction as well as operation and maintenance, refer to [http://ec.europa.eu/echo/files/evaluation/watsan2005/annex_files/SILSOE/SILSOE1%20-%20Iron%20Reducing%20Filter%20-%20Tyrrel.pdf Interim Design, Construction and Operation Guidelines for a Biologically-Enhanced Iron Removal Filter for Attachment to Handpumps].
==Acknowledgements==
* [http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CKoBEBYwAQ&url=http%3A%2F%2Fwww.itnphil.org.ph%2Fdocs%2FIron%2520Removal%2520Filter.PDF&ei=PT_ZT8vKBOjD2QWp942rBw&usg=AFQjCNFNm2C1AYQdDm5RCYXIYTiSApR4yg&sig2=cZ3xdyp7j_aozRydD4jLGg IRON REMOVAL FILTER.] PHILIPPINE CENTER for WATER and SANITATION.
