Recent Experiments

We have done a few experiments this month to try and improve the drilling and rope pump performance.

One experiment that we tried last week was to chlorinate a borehole with a slight manganese/iron problem.  There is not much you can do about manganese - it is a dissolved mineral.  You can oxidise it and it will precipitate into solution - but the particle size is so small it is almost impossible to filter out.  I should add that manganese and iron in the water here is a common occurrence and its presence in boreholes seems to be a random thing - boreholes next to each other - one can have it and the other not??? Very puzzling.  Anyway these minerals are not harmful in the concentrations found here, but they do create an unpleasant taste and odour.  Another association is that a particular type of bacteria likes to munch on manganese/iron and in the presence of oxygen it can really proliferate and form a slime over the pipes - causing a discolouration of the water and bad odour.  We had this occur at one well at Idete, and after cleaning the well by flushing, the water returned to a crystal clear state and odour free.  Another treatment to kill the bacteria would be to use chlorine.  We tried this at the Mapanduzi Primary School - but it appears that the problem is not bacteria but actually manganese and iron.  The chlorine oxidised the minerals and produced brown water that would be impossible for us to filter here.  The water will clean back to its original state as the Chlorine is expended over the next few days - though it seems for this well the water will continue to have a slight metallic taste.

Post chlorinated water.  The iron/manganese has been oxidised and precipitated out of solution.

The water should clean up in a few days time.  We were hoping the problem was iron/manganese bacteria, but it appears to be dissolved iron/manganese minerals which are giving a slight metallic taste to the water.

Another experiment we tried this week was at the Kilongwili School.  I wanted to try using a 1" rising main.  This pump had a 1/2" rising main.  We had not tried a 1" rising main before.  We are now using 3/4" rising main as standard for our installations here - we are also converting all the pumps with 3/4" risers with a larger and stronger 6mm rope.  Previously we used a 4mm rope, but the lifespan of the rope was only a few months before it would break - not good in my opinion - the rope should last 6-12 months at the least.  I was interested to see how a 1" would go. We were using an 8mm rope for the 1" pipe - there was no way this rope was ever going to break!!!  We also were trying out our new guide block design.

The test went well.  We were able to pump a lot of water for not much effort, though I do think it is a bit much for the really small children - the weight of the rope alone is quite hefty.  We did run into a problem though - each time we pumped, after about 30 seconds, the rope would jam.  At first we thought it might be a problem with the pistons being to large.  We reduced the size some of them, but the problem still persisted.  It is apparent that something is at the bottom of the borehole and is being drawn into the intake of the 1" pipe and is causing a jam.  We got an indication of something problematic down there when we pumped out a 0.5m section of rubber.  This well is controlled by the School and they provide free water and no supervision of the well.  We think children have likely thrown things down the small rope hole.  We packed up our 1" rope and rising main and explained that we will have to try and clean out the borehole.  It will require some thought how to do this.  We have told the school that it will be their responsibility to pay for the cleaning - and I have suggested that they should charge a small fee per bucket of water which will help them pay for a guard to watch over the pump and also pay for future upkeep of the well.

The original 1/2" guideblock.  See the wear on the turn-pipe, the rope has worn a hole through the steel!  We need to improve the design of these guide blocks.

A new design we are trying.  Here we have a 1" guide block and thick 8mm rope.  The rope passes around a PVC bush.

Here Raphael gets some help from the local children in installing the 1" rising main.

Boys show off their truck.