Today we got our test results back from the laboratory. Truth be told I was a little nervous. What if the filters didn’t remove any bacteria? What if …. A million little questions whirled through my mind as I opened the laboratory report.

This is what the tests told us:

Testing run 1:

Filter removed 60% of faecal coliforms from water sample. Certainly not yet a functioning filter but ample proof that we are on the right track.

A sterilized sample actually picked up bacteria when it was passed through a filter that had already been swabbed with alcohol. This is not surprising as filters had been stored on the ground for months in tropical conditions. Next time we will boil the filters prior to use. Research says 20 minutes is a good duration.

The taste of water was not negatively changed by passing through the filter.

The flow rate through the fastest filter was 5 litres per hour. Through the slowest filter it was 800 mls per hour.

Testing run 2 – three filters were tested. Prior to testing the filters were boiled for 20 minutes:

Boiling the filters for 20 minutes prior to use killed all bacteria in the filters.

The filter with a flow rate of 5 litres per hour did not appreciably remove bacteria from the water sample.

The filter in double configuration (see images) removed 70% of faecal coliforms from the water. The flow rate slowed considerably as the filter became blocked with the sediment in the water sample. For next time we are investigating a pre filter that can remove the larger sediment from the water before it passes through the filter.

The filter with a very slow filtration rate (less than 100ml per hour) removed approximately 60% of faecal coliforms from the water sample. This filter too suffered from clogging due to the sediment build up as the water sample passed through.

So you can see that we are now removing about 70% of the faecal coliforms from contaminated water samples. This needs to be increased to 95% in order to function as a filter. There is also a need to remove sediment from the water before it passes through the filters.

Now we are back out to Nou Kham’s to make the next batch of filters. With a spring in our step, we certainly have more challenges to overcome but its reassuring to know we are on the right track.

Until next time.