Problems with IM2 hand pumps due to a high iron content in groundwate​r?

Dear Sarah,

High iron can come from two possible sources:

1) The aquifer

2) Corrosion of IM2 riser pipes and rods

IM2 pumps that use galvanised iron (GI) riser pipes and rods are prone to corrosion in aggressive groundwater conditions (where the pH is below 6.5). The corrosive action of the groundwater causes pipes to rapidly rust resulting in release of iron into the water, formation of leaks in the pipes and joint failure. The high iron is unpleasant to users and although there is no direct health impact, it can cause users to abandon sources and seek alternative (often less safe) options. It also causes rapid pump failure.

It is possible to trace the origin of the iron by using a Palintest colour comparator kit with Iron MR1 and MR2 reagents. You take a sample at the beginning of pumping (very early in the morning) and take samples every 30 min of continuous pumping for 2 hours. If you see iron concentrations reduce over that time it is coming from materials in the pump. If you see iron concentrations remain constant at a high level for the duration of pumping it is most likely coming from the aquifer.

The corrosion issue has been known about since the 1980s but because implementers generally tend to install pumps and walk away without any followup with communities it has gone unchecked for a long time. There is sometimes an assumption that the iron comes from the aquifer so some implementers have installed iron treatment plants onto the end of pumps to remove the iron. This seems ironic since it was possibly them who introduced the iron into the borehole in the first place.

If the problem is identified as emanating from the GI rods and riser pipes an alternative is to use stainless steel riser pipes and rods (of the right grade). These can be procured from some of the big pump manufacturers in India (APEX, Ajay etc.).

Vinny

Hi Sarah

Just to clarify a previous answer. In my experience of testing some handpump supplies in Uganda, high dissolved iron can originate from corrosion of GI riser pipes. There is documentation of this, notably an extensive study undertaken in West aftrica in the 1980s and documented by Langenegger (1992). A copy is available on the RWSN website https://rural-water-supply.net/en/reso....

Regards

Lawrence

Dear Sarah,

I agree with Lawrence; iron originating from the corrosion of GI rods and pipes can also occur in dissolved form and not be immediately visible to the eye until subsequent oxidation. In other words, if you pump the water and it is initially clear but turns cloudy later, the source of the iron is not necessarily coming from the aquifer. It is possible that this dissolved iron originates from corrosion of pump materials. This observation is based on experience of the problem with IM2 handpumps and methods for diagnosing the origin of iron in Uganda.

The groundwater in the area where you are working may be considered to be non-corrosive, evidenced by nuetral pH values (around 7). This does not discount the possibility of corrosion. The quality of GI pump parts available on the market at the moment is so poor and loosely regulated (with many components verging on counterfeit) that corrosion can occur even if the pH of groundwater is neutral (non-aggressive). Again, this is based on experience of observing the quality of IM2 pump materials imported from India and China onto the open market in Uganda.

It may be that high iron IS coming from the aquifer. You will be able to diagnose the origin using the simple test set out in my previous response.

High iron in the aquifer will not in itself cause pumps to break down. Iron metabolising bacteria that derive their energy from oxidising dissolved iron may produce a slime that clogs up the pump pipes and cylinder, affecting pump performance. The evidence for this is discussed in a study by Fader (2012).

In summary:

1) Iron may be coming from corrosion of the GI pipes or from the aquifer.

2) You can use the test in my previous reply to diagnose the origin. Additionally you can open the borehole and pull the pipes out to look for evidence of corrosion.

3) If high iron is coming from the corrosion of GI pipes it can occur in dissolved (clear) form AND/OR in oxidised precipitate form.

4) The quality of many GI pipes is so poor these days that they even corrode and leak in non-aggressive groundwater conditions.

5) Bacteria that feed on dissolved iron (originating from the aquifer or from the corrosion of GI) may form a thick slime which could block up the pump cylinder.

6) High iron in itself will not damage the pump. Corrosion of sub-standard materials or clogging by iron metabolising of bacteria will.

7) The best way to find out what is breaking the pumps is to remove the down the hole components and take a look. Iron may not be related to the problem at all.

Cheers,

Vinny

Sarah,

You've got some excellent answers here from Vinny and Lawrence. As Vinny said, your most strategic starting point is to remove and examine the pump components. Heavily corroded (rusted) riser pipes and rods are indicative of aggressive groundwater and may be the source of your high iron. I will point out though that many older (30+ years) boreholes may have iron casing, which could also be an iron source (though there is no easy fix for this problem). Otherwise, the aquifer may indeed be the source of naturally-occurring iron, which is unlikely to damage pumps but can have a significant effect on users perceptions and preferences for using the borehole.

The testing process that Vinny described above is a very good one and a relatively simple way to help determine the source of iron. The idea is that if iron is emanating from corroding components, you will see iron concentrations reduce along with excessive pumping as water that has been sitting in the borehole (and receiving iron as a corrosion byproduct) is replaced with water from the aquifer.

You also might want to look into this: best practices for drilling would include water quality testing (including iron), so you should determine if such information is available from the original implementer, the well driller, or possibly the government if there is a system for such records. Unfortunately though, this data is not always reliable, as I have seen from experience in Uganda. However, it is something worth looking into.

Additionally, if your organization is currently or will be implementing more borehole water points, it would be prudent to ensure that testing take place at the time of drilling and documented within a drilling report that is retained and (hopefully) integrated in to government records. This will help you in choosing the proper pump components and thus preventing unnecessary financial burdens on whoever is responsible for O&M of the borehole in the future.

Good luck!

Jake