So when we say ‘we have tested another batch of filters’ what do we actually mean? What do we do? Please allow me to elaborate on how we create a rudimentary testing lab in very rustic conditions. What follows below is an ordered list of the steps that we follow.

1. Collect some dirty contaminated water. It must have faecal coliform bacteria in it. We have experimented with: cow poo (fresh), water form a dirty puddle by the side of the road, green swamp water, and water with a few drops of juice from raw pork meat (if smell was any indicator, this one is by far the most contaminated). The aim is to have a sample of water highly concentrated with bacteria but that is still relatively clear. This is because our testing laboratory has informed us that clear water is easier for them to test. Yes facilities are limited here!
2. Buy five of the highest quality bottles of drinking water we can find. These are used for transporting test samples, providing a check that the laboratory is applying adequate hygiene practices, and that the filters are fully sterilised.
3. Sterilise the filters, and the jar that will be used to collect the water from the filter. Filter and collection jars are also boiled in between collecting samples.
4. Move the filters hygienically into the filtering harness you have seen in the pictures.
5. The filter is now ready for use. The first sample passed through is straight from the bottle of clean drinking water. Once analysed, this will tell us if we are properly sterilising the filters.
6. Once the required amount has been collected in the cup at the base of the filter this is poured into one of the, empty but still uncontaminated, drinking water bottles.
7. The next sample is the dirtiest contaminated water we can find.
8. The last sample tested is dirty water double filtered by two filters stacked one atop the other.
9. The five samples are labeled and marked as below:

• A straight clean sample that has not been through the filter. This allows us to confirm that the testing laboratory is reliable. We know that if a clean sample comes back as having bacteria in it there is a fault with the laboratory’s testing process.

• A straight dirty sample that has not been through the filter. This allows us to register a baseline for the number of bacteria in the water.

• A clean sample that has been through the filter. For reasons stated above.

• A dirty sample that has been through the filter. Percentage filtration rates are then obtained by comparing the bacteria number in this sample with the bacteria number in the dirty sample baseline above.

• A dirty sample that has been double filtered.

The five samples are then placed in a refrigerated bag and transported to the laboratory for immediate testing.

When each filter is tested we also time how long a measured amount of water takes to pass through so we can calculate flow rates and record them for future reference.

So that is how we are testing the filters currently. Needless to say, we will send the filters off to an International quality testing laboratory to confirm that the filters are adequate before they are ever used in villages.