filter water quality


other DIY filters


As part of EauPropre I ProperWater the low tech water purification system would be connected to the rain harvesting pavilion. This led to some technical specification: the system had to be mobile and compact, had to work with changing flow rates, and be able to filter rain-water at the simple request of passers-by/visitors, without ha­ving to make them wait too long.

Therefore (and much to our regret) the following plans had to be abandoned. These methods were too slow, too uncertain or required electricity or constant care.

We decided to list them here below, just for the fun of it:

→ Sand filters

→ Helophyte filters

→ Ceramic filters

→ UV-filters

→ Mycofiltration

→ Mussels filters


Sand filters

Sand filters and pebble filters remove large impurities and visible particles from water. They make troubled water clear. A disadvantage is that the filters often have to be “backwashed” (sending water through in the opposite direction to remove dirty particles), which wastes a lot of water.

Slow sand filtration, however, is a completely different case. The combination of sand, water and different small (organic) particles generate a layer of biological activity. After being submerged for 2 to 3 weeks, a “benign active layer” of bacteria, algae, protozoa etc. contribute to the purification of water. The slower the water goes through, the better. No need for backwashing here. Maintaining the filters is done by every few months scraping away the top bio-layer. Disadvantage of slow sand filtration is the fragile equilibrium of the whole system. Fluctuating temperatures or irregular flow through the sand layer – as is the case of the ProperWater­Pavilion – disturb the balance between benign microorganisms. This can turn the filter into a polluter.




Plants or helophyte filters

The roots of certain plants turn out to have an amazing filtration capacity. At least, that is when they are allowed the time to create in the sand and pebbles around their roots an ideal living environment for saprotrophic fungi and their friends bacteria that put in a helping hand in water purification. The saprotrophic fungi break down organic water pollution into small molecules feeding the helophyte plants whose roots suck up the small molecules. In turn, the plants give oxygen to the sand, keeping the bacteria healthy. Perfect allies in perfect symbiosis.

Source de Friche
Green Water Treatment Handbook:





You can make ceramic water filters yourself with a combination of clay, organic burned matter (fine straw, rice bran) and water. After baking, the remaining type of terra cotta has very small holes or micro-pores where the organic matter burned up (on average 0.5micron or one five hundredth of a millimetre – on average bacteria are between 0.2 and 0.5 micron in size).

Ceramic filters work in 2 ways

1. Mechanical: impurities, bacteria or germs don’t pass the small pores in the ceramic or attach to them (indirect sediment). The smaller the pores, the better the filter works, so ceramic filters are quite slow.

2. Silver treatment of the filter: The silver layer causes a biocide or chemical attack on microbes. Most bacteria do not survive contact with silver. This would remove up to 98% of harmful substances that contaminate water. Ceramic filters can be used for up to one year. In case of troubled water, the filters need to be cleaned on a regular basis.

Potters for Peace (start watching at 6 min)
Potters without Borders




UV-light, (like the sun) is often used as an alternative to chlorine (in some countries, like the Ne­therlands, chlorine is no longer allowed for disinfecting tap water).

UV.C radiation (one of the three types of UV light) in principle kills all living creatures. The ozone ­layer, however, filters UVC light, so it does not bother us too much on earth. In a protected environment like a stainless steel casing, UV.C can be harnessed to kill bacteria and microbes. When the light penetrates the cell walls of the organisms, it alters their genetic structure. Something few microorganisms will survive. Obviously, a lot depends on the intensity of the light and exposure time. A UV lamp was used in the first Proper­WaterPavilion filter. It turned out that some bacteria want their own personalised UV killer lamp. To fight down our most stubborn enemy (E. Coli), we would have to use not one but five lamps, something our low-energy pavilion was unable to do.




Mushrooms – Mycofiltration

One of the world’s oldest orga­nisms, fungi or mushrooms, turns out also to be one of the world’s most impressive cleaners. Wherever you see one mushroom above ground, underground is an impressive and unexpectedly large web of mycelium threads, the mushroom roots. Mycelium feeds from dead and rotting matter and breaks it down to a point where useful substances (humus) remains. This process takes place in or on the surface of soil, but also in water.

As such mushrooms and their roots (mycelia) are networks of biological cleaners that can absorb and digest chemicals, micro­organisms and even heavy metals, oil and pesticides.

Paul Stamets is one of the big advocates of Mycofiltration. Following his lead are now initiatives experimenting with mycofilters to purify run off water from parkings, to reduce the E.coli level in agricultural waste water, to get rid of pesticides and chemicals in water from parks and gardens, or to make grey water (from showers, sinks,etc..) less grey.

As yet, however, mycelium filtering cannot be used to make water fit for human consumption.



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