please enjoy this time-lapse and please accept our apologies for dropping one of the bottles

Building a Frugal Water Filter Lab

Water management lab at the TU Delft CEG building

The day started at 8:45 am at the Civil Engineering and Geoscience building. Surprisingly, with 4 different entrances, it was quite a challenge to find the "Main entrance". After overcoming this hurdle and meeting with the group we got a small tour of the building and lab areas by our lecture on water management Dr. ir. Ralph Lindeboom.

Dirty pond water

In previous lessons about water management, we discussed the essentials of filtering water and the general cycle for water management. With this information, we are further supposed to think about how to make such water management strategies frugal.

We were given a collection of different materials to use to create a water filter as well as being asked to bring along some things from home.  From home, we brought 1 big plastic bottle per group, preferably big, and cotton pads and/or cloth. Dr Lindeboom supplied us with sands of different coarseness, charcoal, seashells, and of course, dirty pond water.


The challenge was for us to decide the optimal way to position the water bottle and to the order and quantity in which we put the different materials in the bottle to create the best water filter. The general consensus was the same. We cut the bottle near the end and placed it upside down (see diagrams). Next, you put the finest materials at the bottom and the bigger materials at the top: fine sand, charcoal, bigger sand and then the seashells. However, some groups experimented with the number of layers or the amount of material they used. We were all left to do our own things, and experiment with our filters

The water we were going to filter was from a close-by canal. As seen in the image above, the initial water is far from clean and clear, had a peculiar odour, and there was even a big bug in the main container from the canal.

As all the groups started to pour this lovely liquid into their filters, some worked better than others. The charcoal was quite dark and made the water turn a nice grey colour once it had gone through the filter once but if you refiltered the result clearly improved. True cleanliness, however, cannot be seen with the naked eye. We also measured the pH levels, parts per million (ppm), salinity, and temperature. all these factors tell us how pure the water really is.  We were provided, by Dr Lindeboom, pH probes, pH test strips, and a temperature and ppm measurement tool. Most groups ended up with a good ph level of around 7 to 7.4 which is pretty neutral. But the ppm was on the higher side at roughly 350, which is a bit risky to drink and the salinity was medium.

To end the session we talked about why we were using the materials and how they help to filter out different things. The bigger dirt, such as the algae, was filtered out by the seashells. The calcium in the seashells helped reduce the pH level, next some of the bacteria and smaller dirt was filtered out by the charcoal. Dr Lindeboom also discussed that you can manipulate the amounts of 'layers' in your filter to be able to manage the speed at which the water flows through it (quicker through the seashells and coarse sand, and slower through the thin sand and charcoal).

On a final note, we learned the general cycle and process to filter water; I think we realized that it is quite simple to make an amateur water filter,  but can we actually drink this water we filtered? Probably not. At least if we were ever in a dire situation by a dirty but still cleanish river with nothing but an empty water bottle and some nice sand and cloth, we could survive.

-Momo & Gabie

Special thanks to our teammates: Vivian, Shanti, and Alesha;
our lecturer: Dr. Ralph Lindenboom;
and the FI4SGD minor for this opportunity

Appendix